Portable electronic device

The invention discloses a portable electronic device, which comprises a front cover plate, a back cover and a circuit board. The circuit board is configured between the front cover plate and the back cover. The back cover is combined with the front cover plate, and comprises a back portion, multiple side portions and a separator. At least one side portion adjacent to the back portion includes a through groove near the back portion and a slit far away from the back portion, wherein the slit is communicated with the through groove, a first antenna unit and a second antenna unit of the side portion are defined by the through groove and the slit. The separator is positioned in the through groove and the slit. Therefore, antennas need not to be arranged inside the portable electronic device and supporting plates need not to be configured for the antennas, so the portable electronic device becomes thinner. Moreover, the back cover forms the first antenna unit and the second antenna unit through the side portions, t