To prevent the generation of arc discharge in replacement of a service component to surely keep safety and disaster prevention.

This power source cut system for a vehicle makes a power supply line nonconductive when a service component (an adaptor 22) to which power is supplied from a power source for a vehicle is mounted on an electric apparatus body (a power source socket 21), and has a power source cut means 26 which makes the power supply line nonconductive when the service component (the adaptor 22) is mounted on the apparatus body (the power source socket 21), and makes the power supply line conductive by completely mounting the service component from a mounting state of the service component on the apparatus body (the power source socket 21).