A USB device for supplying current to a device connected thereto through a USB interface. In this USB device, current values requested by the devices are preset, as detecting current values, in detector registers of current detecting parts. The current detecting parts constantly monitor current values of electric powers supplied to the devices. Each current detecting part compares a related detecting current value with a related supplied current value. If the supplied current value exceeds the detecting current value, the current detecting part informs a current detection control part of abnormality occurrence. The current detection control part sets a bit in a no-good status register, which corresponds to the current detecting part having informed the abnormality occurrence, and interrupts a CPU. In turn, the CPU refers to the no-good status register and specifies the failure device, and interrupts a current supplying path connecting to the failure device.