A mobile phone includes a housing, a circuit board, a side button and a battery. The circuit board is installed in the housing. The side button is installed on the housing in a slidable manner. The battery is installed on the housing for supplying power to the mobile phone and an elastic member is coupled between the housing and the side button. The circuit board includes a control circuit for controlling the operation of the mobile phone. When the side button is triggered, the control circuit produces a control signal. The side button includes an engaging hook for engaging with a recess of the battery so as to fix the battery on the housing.