A USB communication system, a USB device, and a method of error detection for the USB communication system; with which an error of any breaking of physical connection in USB communication can be detected no matter where the breaking happens, and furthermore an error due to logical communication disconnection can also be detected.In a USB communication system constructed by connecting a host apparatus 2 and a card reader 1 with a USB cable 3, the card reader 1 may include: means for executing a bus reset as a preprocessing for setting a logical connection line with the host apparatus 2, means for measuring a time while the card reader 1 is in a bus reset status, and means for executing an operation of interrupting communication voluntarily according to a measuring result of the means for measuring the time.