Abstract: In a push-on switch comprising a moving contact 6 of partial-hemisphere-face-shaped resilient metal diaphragm which is disposed with its periphery on a pair of peripheral fixed contacts 2b,2b in a contacting manner and at its central part apart above a central fixed contact 2a in an isolated manner at normal state,the improvement is made such that the metal diaphragm moving contact 6 has an opening 6a having at least a protrusion 6b with respect to the opening 6a;so that the opening 6a allows air to pass at inversing and restoring motions of the central principal part of the moving contact 6, thereby preventing drafting of dust onto the central fixed contact 2a, and that the protrusion 6b slides on and cleans the surface of the central fixed contact 2a at each pushing down of the central part of the moving contact 6.