A push button switch 1 is so constructed as to disengage the movable contacts 55b, 56b from the fixed contacts 55a, 56a through operation of the push button 2 held in the switch case 3. A first leaf spring 550 is provided in the switch case 3 to act as an opening-biasing means to bias the movable contacts 55b, 56b away from the fixed contacts 55a, 56a. The movable contact 55b is disposed at an end of the first leaf spring 550 and adapted to engage with and disengage from the fixed contact 55a. The first leaf spring 550 is adapted to be at a position where the movable contact 55b is open relative to and disengaged from the fixed contact 55a at zero displacement of the first leaf spring 550.