A support device, holding a connector in a casing, includes a base frame and a positioning frame. The base frame includes a first mount plate having a through hole, the through hole has a first end and a second end, a fastener of the casing is disposed through the through hole, and the connector is disposed on the first mount plate. The positioning frame includes a positioning portion. The positioning frame is movably disposed on the base frame to be in a first position or a second position. When the positioning frame is located in the first position, the positioning portion is located between the first end and the second end of the through hole. When the positioning frame is located in the second position, the positioning portion is not located between the first end and the second end.