An electronic device adapted to be detachably assembled to a lamp holder having a lamp socket is provided. The electronic device includes an adaptor module and a functional module. The adaptor module includes a lamp connector corresponding to the lamp socket, a first connector electrically connected to the lamp connector, and a first engaging member adjacent to the first connector. The functional module includes a second connector and a second engaging member. The second engaging member of the functional module is detachably connected to the first engaging member of the adaptor module. When the functional module is assembled to the adaptor module, the second connector is electrically connected to the first connector.