To provide a structure of a case for a mobile phone that adopts a fitting structure for the circumferential edges of an upper cover and a lower cover causing a resistance in the fitted parts so as to prevent the upper and lower covers from being easily opened/closed and precludes the possibility of intrusion of water drops or dust or the like between both the covers when the covers are closed.

The case structure for a compact mobile phone is characterized in that the mobile phone has an antenna extended externally, incorporates a communication electronic circuit driven by a battery and capable of making a speech from a transmission reception port through transmission reception of a radio wave, and has a display device and keys, a fitting structure is adopted for the circumferential edges of the upper cover provided with the display device and the lower cover having the keys.