A portable electronic device attached to a housing includes a button, a elastic plate and a switch. The housing defines a through button hole. The button includes an operating portion and a resisting portion. The operating portion extends out of the housing from the button hole. The elastic plate is fixed to the housing. The elastic plate includes an arched portion and defines a guiding hole, the arched portion resists the button. The resisting portion is received in the guiding hole. The resisting portion contacts the switch to form an electronic signal when the button is pressed down. The arched portion of the elastic plate pushes the button to return to original position by a rebounding force when the button is released.