PURPOSE: To control the pressing force to a workpiece during conveyance and attract the workpiece of complex shape positively.

CONSTITUTION: A center pole 4 axially movable through a non-magnetic body is provided inside a cylindrical frame body 2 for enclosing a electromagnetic coil 1, and plural yokes 15 movable in the same direction as the center pole 4 are provided at the outer periphery of the frame body 2. There are also provided a first energizing means 13 for energizing the center pole 4 in one direction, a second energizing means 19 for energizing each yoke 15 in the same direction as the center pole 4, and a pressing force limiting sensor 20 for limiting the pressing force of the center pole 4 and yokes 15 to a workpiece 25.