An electronic device includes a main body defining an opening, and a key mechanism secured in the opening. The key mechanism includes a fixing mechanism, a circuit board and a key. The fixing mechanism includes a tab and a support. The tab protrudes from a sidewall of the opening. The support includes an elastic supporting rib connected to the tab. The circuit board is fixed on the support and includes a switch. The key is rotatably connected to the fixing mechanism actuates the switch to generate an input signal. The supporting rib applies a restoring force to the key.