A portable electronic apparatus is connected to a power supply device via a transmission line, and it includes a designated connector, a charge control circuit, and a judgment circuit. The designated connector includes five terminals respectively corresponding to five pins of a USB connector of the power supply device. When the power supply device is connected to the portable electronic apparatus, the first terminal of the designated connector is logic high, the fourth terminal of the designated connector is logic high, and the third terminal of the designated connector is logic high after pulling up the voltage level of the second terminal, the judgment circuit pulls down the voltage level of the third terminal and detects the voltage level of the third terminal so as to generate a determining result for determining a type of the power supply device.