An image forming device comprising: an attachment part to which an exchange unit having (i) a fuse that can be molten by being supplied with an electric current and (ii) a voltage signal output part that is connected to the fuse is detachably attached and the exchange unit being either a genuine product or a non-genuine product; and a control part that is configured to apply a conduction signal to the fuse and to detect whether or not the fuse is blown based on the voltage signal output from the voltage signal output part corresponding to the conduction signal, the image forming device is characterized in that the conduction signal is a signal string in which a first conduction signal and a second conduction signal are strung together; the first conduction signal corresponds to a first current supply state where the fuse of the exchange unit being the genuine product is not molten and the second conduction signal corresponds to a second current supply state where the fuse of the exchange unit being the genuine product is molten; the control part is further configured to determine that the exchange unit attached to the attachment part is the genuine product when detecting that the fuse is not molten by applying the first conduction signal in the signal string and also detecting that the fuse is molten by applying the second conduction signal in the signal string, and to determine that the exchange unit attached to the attachment part is the nongenuine product when detecting that the fuse is molten by applying the first conduction signal in the signal string or when detecting that the fuse is not molten by applying the second conduction signal in the signal string. an attachment part to which an exchange unit having (i) a fuse that can be molten by being supplied with an electric current and (ii) a voltage signal output part that is connected to the fuse is detachably attached and the exchange unit being either a genuine product or a non-genuine product; and a control part that is configured to apply a conduction signal to the fuse and to detect whether or not the fuse is blown based on the voltage signal output from the voltage signal output part corresponding to the conduction signal, the image forming device is characterized in that the conduction signal is a signal string in which a first conduction signal and a second conduction signal are strung together; the first conduction signal corresponds to a first current supply state where the fuse of the exchange unit being the genuine product is not molten and the second conduction signal corresponds to a second current supply state where the fuse of the exchange unit being the genuine product is molten; the control part is further configured to determine that the exchange unit attached to the attachment part is the genuine product when detecting that the fuse is not molten by applying the first conduction signal in the signal string and also detecting that the fuse is molten by applying the second conduction signal in the signal string, and to determine that the exchange unit attached to the attachment part is the nongenuine product when detecting that the fuse is molten by applying the first conduction signal in the signal string or when detecting that the fuse is not molten by applying the second conduction signal in the signal string.