A power measuring apparatus includes a line connector connected to a power source line, which supplies power to equipment; and a measuring circuit, which measures a voltage and a current supplied to the equipment by means of the connected power source line. The power measuring apparatus also includes a calculator which calculates, on the basis of the measured voltage and current, power consumed by the equipment; and a transmission line connector connected to a transmission line that transmits data used for the purpose of monitoring the equipment. Furthermore, the power measuring apparatus also includes a transmitter that transmits data indicating the calculated power to the transmission line. Consequently, the power measuring apparatus can be installed in equipment at lower cost than before.