PURPOSE: To suspend a press operation when there is the danger of entering a hand into a dangerous area by detecting the direction of a motion of the hand after turn-on operation by a magnetic sensor in the case of executing press operation by a turn-on operation of left and right start switches.

CONSTITUTION: In a switch box 10, a magnetic sensor 12 for detecting magnetism of a ring which a worker wears on his finger is provided, and also, plural pieces of the same magnetic sensors 13a-13e are provided in the horizontal direction between the switch box 10 and a dangerous area P, a motion of a hand after a start switch 11 is turned on is grasped from an output variation of these magnetic sensors 12, 13a-13e, and when there is a fear that the hand enters the dangerous area P, a ram is reversed and made to ascend.