In a memory system using a storage medium, which is inserted into an electronic apparatus via a connector to add a memory function thereto, the storage medium has a GROUND terminal, a power supply terminal a control terminal and a data input/output terminal, and the connector has a function of being sequentially connected to each of the terminals. When the storage medium is inserted into the connector, the GROUND terminal and control terminal of the storage medium are connected to corresponding terminals of the connector before the power supply terminal and data input/output terminal of the storage medium are connected to corresponding terminals of the connector. Thus, it is possible to improve the stability when a memory card is inserted into or ejected from the memory system.