A key switch structure which enables a reduction in the width of the key switch. A key switch structure comprises a first support member (22), a second support member (23), and a third support member which are arranged independently of each other, the first support member (22) having rotation pins (22d, 22e) and slide pins (22a, 22b), the second support member (23) having rotation pins (23e, 23f) and a circular columnar slide section (23a), the third support member having front end sections (24d, 24e), which are slidably held, and a support shaft section (24a). A key top (21) is supported by the support members (22, 23, 24) so that the key top (21) can move in the vertical direction. The length of at least one side of each of the support members is set to be less than or equal to the mounting diameter of a rubber dome (27).