To automate inspection so as to easily perform inspection by inspecting a normal/abnormal load operation based on a switch content calculated based on control data between units and the fluctuating pattern of at least one of a battery current and a voltage.

A control data collecting means 15A is provided and when controlling is performed by a control means 11A based on control data transmitted and received among units 1 to 7 connected to a multiple bus line L by a communicating means 11B, the content of an operated switch 13 is calculated by a switch operation calculating means 15B. Then, the current and voltage of a battery 21 accompanying the operation of the operated switch 13 are measured by a measuring means 15C and based on the fluctuation pattern of at least one of these, the normal/abnormal operation of a load 14 is collated and inspected by a collation determining means 15D. Thus, complex inspection and the increase of an inspecting time are prevented.