An electromagnetic contactor having normally open and normally closed contact pairs 22, 26 includes a movable crossbar 12 having apertures 14 each defining two guide surfaces 18a, 18b; 18c, 18d inclined at different angles for guiding spring biased movable contact members 16 disposed in the apertures. These inclined surfaces serve to jam the crossbar against the base 10 of the contactor when the crossbar is moved in a direction to open fused contact pairs during the initial spring decompression movement of the crossbar, to thereby prevent the normally open and normally closed contact pairs from being closed at the same time.