An arc detection apparatus (10) includes an arc detection circuit (102), a current transforming unit (128), a current input wire (108) and a current output wire (110). A power supply apparatus (20) sends an input current (Iin_a) to an electronic apparatus (30) through the current input wire (108), and the electronic apparatus (30) sends back an output current (Iin_b) to the power supply apparatus (20) through the current output wire (110), so that the current transforming unit (128) induces and generates an induced current (112). The current transforming unit (128) sends the induced current (112) to the arc detection circuit (102). The arc detection circuit (102) utilizes the induced current (112) to detect an arc.