To provide a power controller which can perform power supply at an appropriate timing.

The power controller including an alternator 60, a high-voltage system battery 31, a low-voltage system battery 11, and a DC-DC converter 20 provided between the high-voltage system and the low-voltage system is further provided with a power supply management ECU 50 for deciding whether the power supply capability on the high-voltage system side is short for demand power of the high-voltage system load and whether the power supply capability on the low-voltage system side is short for demand power of the low-voltage system load, and controlling power supply of the alternator 60 and the DC-DC converter 20 or operation of the high-voltage system load 32 or the low-voltage system load 12 based on the decision results while taking account of the delay of power supply from the alternator 60 or the DC-DC converter 20.