A connecting module, disposed at a casing having a through hole, includes a door, a connecting port and an elastic member. The door is rotatably coupled to the casing so as to be located at a first position to cover the through hole or at a second position to open with respect to the casing. The connecting port is disposed at an inner side of the door so as to be disposed inside the casing when the door is located at the first position or exposed outside the casing when the door is located at the second position. The elastic member is rotatably coupled to the connecting port so as to rotate with respect to the connecting port to fasten a plug between the connecting port and the elastic member when the plug is connected to the connecting port.