A memory card socket structure includes an arm rotatably moved by an insertion and an extraction of a memory card into and from a card compartment and a memory card detecting function for detecting whether the memory card is inserted into the card compartment. The arm includes a main portion to be in contact with the memory card and a sub portion disposed opposite to the main portion with respect to a rotation shaft thereof, and is located at a rear side of the card compartment. The arm is engaged with a torsion spring whose first end portion is engaged with a first stationary contact but whose second end portion is engaged with the sub portion, whereby the main portion is biased by the spring toward an entrance of the card compartment.