PURPOSE: To provide an electronic watthour meter which can be adjusted automatically.

CONSTITUTION: The watthour meter is constituted of a power-to-voltage conversion means 3 which converts electric power to be measured into a voltage signal, a voltage-to-frequency conversion means 4 which converts the voltage signal from the power-to-conversion means 3 into a frequency signal, a processing means and a smooting means 9, 8 which detect the frequency signal form the voltage-to-frequency conversion means 4 in no-load electric power and which convert it into a voltage signal, and a correction means 7 which is installed between the power-to-voltage conversion means 3 and the voltage-to- frequency conversion means 4 and which corrects the voltage signal of the power-to-voltage conversion means 3 on the basis of the voltage signal from the smoothing means 8.