An electronic device includes a Printed Circuit Board (PCB), a housing, an inner cover, and an outer cover. The PCB mounts a first socket and a second socket thereon. The housing includes a first slot disposed to correspond to the first socket and a second slot disposed to correspond to the second socket. The housing receives the PCB. The inner cover opens/closes the first slot. The outer cover opens/closes the second slot. The first socket and the second socket are open toward the first slot and the second slot, respectively. When the outer cover is open, the inner cover is exposed and is in an openable state.