PURPOSE: To obtain an invariably excellent contact state in a reading and writing device for a plate type storage medium which incorporates a semiconductor storage circuit by pressing a storage body back to a specific position with position specifying members right before the storage body is locked to a base.

CONSTITUTION: The bottom plate 13 of the base 2 is cut in three ways except the inner side to form a cantilever beam 14, and the projection piece which have a slanting part 15a having the inner side slanted downward at the tip and a flat part 16b at the front side is implanted where the front side end part of the plate type storage medium contacts the slanting part 15a while the plate type storage medium is loaded nearly normally in a pocket member 5, thus constituting the position specifying members 12 and 12 provided at two positions of the base 2. A recessed part 17 is formed in the reverse surface of a top surface 4 that those position specifying members 12 and 12 face, and the storage body 1 is moved downward to such an extent that the storage body 1 is unlocked when spread.