A portable electronic device includes a main body, a battery, and a battery fixing mechanism including a button disposed through a button hole of the main body, first and second rod members, a first linkage rod pivoted to the first rod member and disposed in an oblique slot of the button, first and second transverse elastic members, and a rail member having transverse, oblique, and incurve rails. When a protruding rod of the first rod member moves in the transverse, oblique, or incurve rail, the rail member moves longitudinally to make the first rod member move transversely to be engaged with or separated from a first fixing hole of the battery. The first and second transverse elastic members are respectively disposed on the first and second rod members. The second rod member abuts against the first rod member for pushing the first rod member when the button is pressed.