A determination circuit includes a first detecting unit that detects whether first and second power-supply terminals are connected based on a voltage at the second power-supply terminal of a coupling unit that includes the second power-supply terminal connectable to the first power-supply terminal of a device including first and second terminals, and third and fourth terminals connectable respectively to the first and the second terminals. The determination circuit also includes a voltage applying unit that applies first and second voltages to the third and fourth terminals respectively, a second detecting unit that detects that the first and the second terminals are connected to the third and the fourth terminals, respectively, and a discrimination unit that discriminates a type of the device based on voltages at the third and the fourth terminals connected to the first and second terminals, respectively.