An electrical wiring device for vehicle includes a distribution module that is disposed between an auxiliary connector and optional devices. The distribution module includes: semiconductor relays connected to a power supply line; input/output interfaces; a control unit configured to control the semiconductor relays and the input/output interfaces on the basis of various kinds of signals acquired via a communication line; and a connecting terminal for connecting outputs of the semiconductor relays and outputs of the input/output interfaces to the optional devices. The control unit controls operations of the semiconductor relays and the input/output interfaces corresponding to the optional devices connected to the connecting terminal.