To provide an inhibitor switch capable of suppressing oil stagnation in a case and preventing a stationary contact from short-circuiting.

The inhibitor switch 1 equipped with an electrode board 3 having stationary contact on its vertical wall 9, a movable board 5 having a movable contact slidable to the stationary contact and capable of moving along the vertical wall 9 of the electrode board 3, and the case 7 covering the side with stationary contact, and the movable board 5 in such a way as supporting fast the electrode board 3, extended in mating with the movement of the movable board 5 and having a slit 15 to admit protrusion of a drive pin 13 of the movable board 5 coupled with the side with a manual valve is installed inside a transmission case in which the oil of an automatic transmission spatters in such a way that the vertical wall 9 is rising and senses the shift position of the automatic transmission by the movable and stationary contacts, wherein the case 7 is arranged so that the upper edge 31 of the slit 15 is protruded to the outside of the case 7 farther than the lower edge 33.