To indicate various energy source in single representation by indicating the used amount of energy sources, e.g. electricity or gas, integrally with the same index.

Used amounts S1-S3 of various energy sources, measured with different units by means of a plurality of meters 2-4, are converted with identical unit and the converted amounts of used energy S4-S6 are indicated. Since the used amounts of energy sources, e.g. electricity or gas, can be indicated integrally with same index, an energy meter 1 very useful in view point of energy management can be realized.