A switch device including a case having a through hole, a cylindrical member including a first cylindrical section having a small diameter arranged in the through hole of the case and a second cylindrical section having a large diameter arranged on an outer portion of the case, an operation member including a shaft section slidably inserted into the first cylindrical section and a head section slidably arranged in the second cylindrical section, a waterproof member provided between an inner peripheral surface of the second cylindrical section and an outer peripheral surface of the head section, and a vent passage that allows air inside the second cylindrical section and air outside the case to pass through a vent hole provided in the cylindrical member and a gap between an outer surface of the cylindrical member and an outer surface of the case for ventilation.