Abstract: 
The present invention is provided with: a voltage value calculation means for calculating the voltage value of an alternatingcurrent voltage; a voltage zerocrosstime calculation means for detecting the zero cross of the alternatingcurrent voltage and calculating the time from a start point determined on the basis of a reference timing signal to the zerocross of the alternatingcurrent voltage; an electric current value calculation means for calculating the electric current value of an alternating electric current; an electric current zerocrosstime calculation means for calculating the time from the start point to the zerocross of the alternating electric current; an electric power calculation means for calculating the phase difference of the alternatingcurrent voltage and the alternating electric current on the basis of the time until the zerocross of the alternatingcurrent voltage and the time until the zerocross of the alternating electric current and calculating an electric power on the basis of the voltage value, the electric current value, and the phase difference; and a reference timing transmission means for transmitting the reference timing signal. The phase difference necessary for calculating the electric power is calculated on the basis of the time until the zerocross of the alternatingcurrent voltage and the timeuntil the zerocross of the alternating electric current from the start time determined on the basis of the reference timing signal, and the voltage and the electric current can therefore be measured separately.
