An electronic device includes a chassis, a main board module and an electrically connecting module. The chassis is slidably disposed in a rack. The rack has an electrically connecting terminal. The main board module is disposed in the chassis. The electrically connecting module includes a circuit board and a first connector. The circuit board has a first connecting end corresponding to the main board module and a second connecting end corresponding to the rack. The first connecting end is electrically connected to the main board module. The first connector is disposed on the circuit board and electrically connected to the second connecting end. When the chassis is in the rack, the first connector is electrically connected to the rack. When the chassis is pulled out from the rack, the first connector is moved with the chassis such that the electrical connection between the first connector and the rack is terminated.