A switch unit including a case that has an opening and a switch, two terminals that partially project to an outside of the case from the opening, a gasket configured to seal the opening, the gasket including two through-holes through which the terminals extend, a base member, and a pressing member that is arranged between the terminals, where the gasket is in close contact with the terminals at the through-holes, a region between the through-holes of the gasket is pressed while nipped between the pressing member and the base member, and a surrounding region in the gasket is pressed while nipped between an inside surface of the case and the base member.