To provide an inhibitor switch that surely operates, by suppressing oil stagnation at an electrode board using a simple structure and preventing shortcircuiting.

The inhibitor switch is equipped with an electrode board having a plurality of stationary contacts S2, VB, S4, S1, S3 and a circuit for external connection and a movable board having a movable contact, installed in a transmission case in which an oil for an automatic transmission spatters, and senses the shift position of the automatic transmission by the movable and stationary contacts, wherein the electrode board 3 is furnished with recesses 29 of such a configuration that a back wall 63 stretching in the longitudinal direction is surrounded by surrounding walls 65, 67, 69, 71 located upper and lower and on the left and right, and on the side with back wall 63, the circuit is supported in embedded condition, and also parts 73, 73, 77 of different circuitries of the circuit are exposed on the insides of recesses 29, etc., and an exhaust slope 61 for exhausting the oil having intruded to the inside of the recesses 29, etc., is provided on the surrounding wall 67 below the recesses 29 in such a way as inclining downward outside the recesses 29, etc.