A power strip includes: jack portions; current meters each configured to measure a current being supplied from the corresponding jack portion to one of external electrical devices, and to output a measurement signal corresponding to a magnitude of the current; and a computing unit configured to obtain instantaneous values of the current at a plurality of time points on the basis of the measurement signal, and to calculate a power value using the instantaneous values. The computing unit configured to obtain the instantaneous values-of the current by using any one of a first zero point and a second zero point as a reference.