A small and thin storage device that can be substituted for IC memory card is disclosed. When the recording medium cartridge is inserted into the frame of the storage device, a slide member in a hub moves parallel to the frame and retracts a shaft under restriction of a restriction member provided in the recording medium cartridge so that the hub and the shaft engage. When the recording medium cartridge is ejected from the frame, the slide member moves parallel to the frame and the shaft under restriction of the restriction member so as to release the engagement of the shaft and the hub.
