PURPOSE: To prevent any malfunction from occurring as well as to improve stability and reliability operation by detecting the size of a load current in order at each specified time interval at the time of opening or closing a windowpane, and driving it in comparison between the deviation value and the reference value.

CONSTITUTION: When a close button of an operating part 32 is operated and a close operation is carried out at the time of fully opening a windowpane, the size of a load current 1 flowing in a drive motor 3 is detected in order. At that time, the deviation value X of detected value data is found at specified sampling time interval, comparing it with the set reference value Y, and if it is normal, the windowpane is lifted. Since it goes beyond the reference value Y at the full-close position, an overcurrent detecting signal So is given to a judging part 46, feeding a control circuit 31 with a stop command, thus the drive motor 3 is stopped. In succession, during closing operation, when hands and so on are pinched, an overcurrent is detected, but a microswitch 23 is in a state of being turned to OFF so that it is so judged as something wrong, thus a trouble processing command is given to the control circuit 31. In addition, the drive motor 3 is rotated in reverse and an opening operation process takes place, and then hands the like are removed.