A charging socket has a base and a holding body covering the base. The holding body has an opening receiving recess, and a first holding plate. A gear element has a ring-like body mounted in the base. The ring-like body has gear teeth at an outer periphery thereof, and a connecting portion connected with the base by a connecting spring for forcing the ring-like body to rotate. A swingable arm pivoted to the base has a ratchet tooth engaged with the gear teeth for stopping the ring-like body from being pulled by the connecting spring to rotate. A movable element has a basic plate slidably received in the receiving recess, and a second holding plate. A side of the basic plate is connected with a rack parallel to a sliding direction of the movable element and is lower than a bottom of the basic plate, engaging with the gear teeth.