To improve an anti-coming-off effect of a cable while enabling to facilitate a fixing work in a comparatively simple structure.

A connecting connector for an AC adapter to which a cable connector 11 for an AC adapter power cable 10 is plugged in and connected is provided at a lower part of the rear face part of a main body case 2 of an IC card reader/writer 1. To the main body case 2, is provided a metal thin plate fixing member 17 with a mounting part 18 arranged along its bottom plate part 2a and a locking part 19 for locking an insulation part 11a of the cable connector 11 connected to the connecting connector with a U-shaped notched part. By screwing down the fixing member 17 to the bottom plate part 2a through a long hole formed at the mounting part 18, the locking part 19 is capable of displacing between a retreat position (a) for the locking part 19 to retreat into and an anti-coming-off position (b) for locking the cable connector 11 in a state free from coming-off, and furthermore, can be fixed at the locking position.