To detect adhesion of a contactor quickly while neglecting the discharge state of a capacitor.

The power unit for a vehicle comprises a battery 1 which supplies power to a motor 53 for running the vehicle, the contactor 3 for connecting a contact 10 to the output side of the battery 1 and having an excitation coil 11 for turning the contact 10 on/off, a control circuit 4 for turning the contact 10 on/off by controlling conduction of the excitation coil 11 of that contactor 3, and a circuit 5 for detecting adhesion of the contact 10 of the contactor 3. The adhesion detection circuit 5 has a judgment circuit 17 for detecting the inductance of the excitation coil 11 of the contactor 3. In the power unit, the control circuit 4 controls the excitation coil 11 of the contactor 3 to nonconduction state, the judgment circuit 17 detects the inductance of the excitation coil 11, and the adhesion detection circuit 5 judges adhesion from the detected inductance.