Excel で第2軸を追加する
小さい系列をクリックし、「データ系列の書式設定」で第2軸をオンにします。「グラフの種類の変更 > 組み合わせ」で一方を折れ線にして第2軸に割り当てる方法もあります。Google Sheets ではグラフエディタでその系列の軸を右軸にします。一方が数万の売上、もう一方が比率や小さな件数のときに第2軸が必要です。
目次
要点
小さい系列をクリックし、「データ系列の書式設定」で第2軸をオンにします。「グラフの種類の変更 > 組み合わせ」で一方を折れ線にして第2軸に割り当てる方法もあります。Google Sheets ではグラフエディタでその系列の軸を右軸にします。一方が数万の売上、もう一方が比率や小さな件数のときに第2軸が必要です。
確認のポイント
8行の売上では合計 24450、東 9450、東の比率は 0.38650306748466257、Widget の比率は 0.8098159509202454 です。売上と同じ 25000 までの軸に描くと、比率は基線に張り付いてデータが無いに見えます。第2軸は数値自体を変えず、東の比率は 9450/24450 のままであるべきです。
注意点と互換性
両方の軸にタイトルを付け、金額と比率を混同しないようにします。同じ単位の系列を、プロットを埋めるためだけに2軸に分けないでください。右軸の頂点が 9450 なら売上を第2軸に置いた誤りで、38.65 なら比率を 0.3865 ではなく百分率で持っている可能性があります。円グラフに第2軸はありません。
英語の詳細例・数式・著者メモ
Excel How-toTested in: The totals and shares used as the two-scale example were evaluated in Google Sheets on 12 November 2026. Excel 365 menu names are the current desktop labels; I did not click through Format Data Series or the chart editor this session.
How to make a basic column, line, or pie chart is in How to Make a Chart in Excel. This page is only about a second vertical axis.
When you actually need a second axis
On the eight-sale sample, Revenue goes up to a grand total of 24450, and East is 9450. East’s share of that total is 0.38650306748466257; Widget’s share is 0.8098159509202454. If you plot Revenue and those shares on one axis that runs to 25,000, the share series sits on the baseline and looks like it has no data.
A second axis is for that mismatch in scale, not for a second category axis (dates vs text). If the axis is showing serial numbers such as 45299, that is a format problem, in chart dates showing as numbers.
Add the axis in Excel
- Create a chart that includes both series (for example Revenue as columns and Share as a line).
- Click the Share series (the small one). If it is hard to click, use Chart Design > Select Data or the Series drop-down on the Format pane.
- Right-click the series and choose Format Data Series.
- Under Series Options, select Secondary Axis.
- A vertical scale appears on the right. Set its number format to a percentage if the series is a share.
- Optionally use Chart Design > Change Chart Type > Combo to make one series a column and the other a line, and assign the line to the secondary axis in that same dialog.
Add an axis title on both sides (Chart Elements > Axis Titles) so a reader can see which scale is money and which is a percent. Do not force two series of the same unit onto two axes just to fill the plot area — that makes a 9450 and a 24450 look similar in height when they are not.
Add the axis in Google Sheets
- Open the chart editor.
- On the series you want on the right, set Axis to Right axis (under Customize > Series, or in Setup depending on the build).
- Format that axis as a percent if needed.
If Right axis is not offered, change the chart to a combo (columns plus a line) and try again. Some chart types, including pie, have no second axis.
Check the plotted numbers
The right axis does not change the underlying values. East’s share should still be 9450 ÷ 24450, which in the test workbook was 0.38650306748466257. If the line peaks at 1, you may have plotted the share correctly; if it peaks at 9450, you put Revenue on the right axis by mistake. If it peaks at 38.65, the series was stored as 38.65 instead of 0.3865 — format the axis to match the way the number is stored, or divide by 100 in a helper column.
A pivot already has the share if you used Show Values As % of Grand Total. You can chart that pivot, or compute the share next to the source with =B2/$B$10 and chart the helper column.
Once both series use a readable scale, confirm the category axis is still the one you intended (months, products, or regions) and that a legend names each series and, if the titles are short, which axis it uses.