A portable electronic device (100) includes an upper housing (40), a circuit board (10), a display (12), a battery (14), and a lower housing (20). The upper housing defines a display section (424) therein. The circuit board has a top surface (11) and a bottom surface (13) at an opposite side of the top surface. The display is seen outwardly through the display section. The battery and the display are formed adjacent to each other on the top surface of the circuit board. The circuit board, the battery and the display are placed in-between the lower housing and the upper housing. The upper housing is detachably mounted to the lower housing for detachably holding the battery.