The present invention provides a key switch diaphragm capable of obtaining a good click feeling and capable of avoiding contact failure and having a high durability. A key switch diaphragm 30 comprises a thin plate having flexibility and conductivity, and the key switch diaphragm 30 includes a truncated pedestal 16, and a spherical domical portion 18 being raised toward an upper portion of the pedestal 16 on the side of the upper portion of the pedestal 16. The domical portion 18 is provided at its substantially central portion with an outwardly raised portion 32 being raised toward an outer surface of the domical portion 18. An edge of the outwardly raised portion 32 on the side of its inner surface forms a contact 34.