To run a vehicle while surely detecting precharge of a capacitor, even if a voltage detection circuit and a current detection circuit fail.

A power supply unit for vehicle includes: first and second contactors 2 connected to positive and negative output sides of a battery 1; a precharge circuit 3 which is connected in parallel to the first contactor 2A, and preliminarily charges the capacitor 21 connected to a vehicle side; the current detection circuit 8 which detects a precharge current when a precharge relay 7 of the precharge circuit 3 is turned on; the voltage detection circuit 9 which detects a voltage difference between a battery side of the first contactor 2A in an OFF state and the vehicle side; and a control circuit 4 which controls the first contactor 2A by signals of the voltage detection circuit 9 and the current detection circuit 8. Moreover, the power supply unit includes a temperature sensor 5 to detect temperature of a precharge resistor 6, and the control circuit 4 controls the first contactor 2A by the temperature sensor 5, and the signals of the voltage detection circuit 9 and the current detection circuit 8.