To ensure accurate detection of the position of a write protecting button by ensuring stable contact/separation movement of contact pieces.

A switch structure comprises a first contact spring piece 20 in a cantilever manner energized so as to put a contact portion at the end of a write protecting button 3 of a card 1 in contact with a recess corresponding to one sliding portion thereof and a second contact spring piece 30 in a cantilever manner energized so as to put a contact portion at the end of the write protecting button 3 in contact with a recess corresponding to the other sliding portion thereof and extending along the first contact spring member 20 in the same direction. In accordance with the contact/separation movement of the first and second contact spring members 20, 30, the sliding position of the write protecting button 3 is detected.