To inexpensively constitute a pinching detector by using inexpensive electronic components.

A voltage monitor circuit 42 for monitoring a between-terminal voltage of a closure motor 41 comprises a first monitoring circuit 43a which is composed of resistances R1a-R3a for voltage dividing, and a second monitoring circuit 43b which is composed of resistances R1b-R3b for voltage dividing. The between-terminal voltage of the closure motor 41, which is monitored by the voltage monitor circuit 42, is subtracted from a battery voltage VB of a battery 36 so that a dropping voltage V3, which is generated by the passage of a motor current through electric wires 45a and 45b, can be computed. In the case where the computed voltage drop V3 is a preset value or above and where a preset and predetermined period of time has passed, it is determined that pinching caused by an opening/closing body 2 is detected.