PURPOSE: To simplify power transmission from a motor to a lifting screw by providing both an electrically driven screw device which is concentrically connected directly with an output shaft for an inverter-controlled multipolar motor and the lifting screw, and a lifting guide device.

CONSTITUTION: A driving motor 1 is a low speed motor, such as an inverter- controlled multipolar motor, and is mounted on a base plate 12. A lifting screw 4 concentrically connected directly with an output shaft for the motor, is in contact with a nut 6 in a nut-sleeve 5 for lifting fixed to a seat 13, and vertically moves the nut 6 and the nut-sleeve 5. A stopper 7 for dropping out is fitted at the end part of the screw 4. A guide 9 fixed to a chair 13 is so formed as to be able to slide in a guide 8 fixed to the base plate 12. The guides 8, 9, the screw 4, the nut-sleeve 5 and the motor 1 are concentrically arranged, and both a stopper for dropping out and a stopper for rotating relatively are provided on the guides 8, 9. When the title device is operated, the rotation of the motor is directly transmitted to the screw, and after it is transmitted to the nut 6 and the nut-sleeve 5, the seat 13 is vertically moved.