A wearable electronic device with a function of detecting a wearing state, comprising: at least one electrode; a capacitance calculating circuit, coupled to the electrode, configured to calculate a capacitance variation generated by at least one of the electrode; and a wearing state determining circuit, coupled to the capacitance calculating circuit, configured to determine the wearing state according to the capacitance variation. By this way, the wearing state can be auto detected and the wearable electronic device can be correspondingly control according to the wearing state.