To provide a push button switch having a simple structure and easy to assemble although its thickness can be reduced.

This push button switch is provided with a base 40 having a rotary electronic component 80 mounted and equipped with a pressing part 47, a mounting member 10, and a switch contact 61 disposed at a position pressed by the pressing part 47 of the base 40. The base 40 is rotatably journalled to the mounting member 10 by engaging a shaft 41 attached to the base 40 with a bearing 33 attached to the mounting member 10. A dislodging prevention mechanism comprising a slit 23 and an engagement part 51 for preventing the movement in the direction releasing the engagement of the shaft 41 of the base 41 with the bearing 33 of the mounting member 10 and a dislodging prevention mechanism comprising a slit 27 and the lower side 42 of the base 40 are formed on the mounting member 10 and the base 40. A rotation stop mechanism comprising an engagement part 49 and a lock part 37 for stopping the base 40 from rotating in the direction separating from the mounting part 10 is formed on the base 40 and the mounting member 10.