Electronic device for reducing audio noise caused from unbalanced ground and mobile communication device thereof

An electronic device includes a first circuit board having a first audio source and a first reference grounding end, a second circuit board having a second audio source and a second reference grounding end, a flexible board cable, a grounding wiring, a selection unit, and a receiver. The flexible board cable couples the first audio source to the second circuit board. The grounding wiring couples the first grounding end to the second circuit board. The selection unit is used for selecting one from the first and second audio sources to output and selecting one from the first and second reference grounding ends to output. An input end of the receiver is controlled by the selection unit to be connected to the first or second audio sources, and a grounding end of the receiver is controlled by the selection unit to be connected to the first or second reference grounding ends.