The invention improves detection accuracy of interposition at a vehicle window. An interposition detector determines that a window at a passenger's seat has interposition if motor current for opening and closing the window at the passenger's seat does not decrease to be less than a predetermined threshold but increases to be not less than a second threshold, or if the motor current does not decreases to be less than the predetermined threshold but increases at a predetermined or more increase rate. The interposition detector determines that the window at the passenger's seat does not have interposition if the motor current is less than the predetermine threshold. The invention is applicable to an automatic window system and the like.