To provide a power monitor which can set monitoring of power consumption at a plurality of time periods and in arbitrary time units for an effective monitoring of the power consumption, to improve deepening of the awareness of energy saving, with a resultant reduction in power consumption.

The power monitor 1 measures the power consumption in the load circuit of a distribution board to monitor whether or not the power consumption exceeds a target set value set in advance, and when the power consumption exceeds the target set value, the power monitor generates an alarm. In the power monitor, the monitoring of the power consumption can be set at a plurality of time periods and also in arbitrary time units.