A side key structure of an electronic device includes a housing, a flexible circuit board, and a side key. The housing defines a receiving groove. The flexible circuit board includes a key switch. The side key includes a main key body, a fastener, and a pressing portion. The flexible circuit board is mounted on a sidewall of the receiving groove. The pressing portion and the fastener are arranged on a same side of the main key body. The main key body is partially received in the receiving groove. The fastener and the pressing portion pass through a second sidewall of the receiving groove. The fastener is mounted within the receiving groove. The main key body is configured to be pressed to cause the pressing portion to press the key switch to activate the key switch.