Abstract: A method for detecting and indicating use state of SATA external storage device includes the steps of (1) providing a SATA external storage device connected to a power input unit; (2) providing a driving circuit that is driven by changes in current flown therethrough, and is connected to and between the power input unit and a SATA storage unit of the SATA external storage device; and (3) providing an indicating circuit that is connected to and driven by the driving circuit. The driving circuit may be a transformer circuit, a relay circuit, or a voltage comparator circuit. The indicating circuit may be a light-emitting diode circuit, a liquid crystal display circuit, or other applied circuits. By utilizing changes in the current flown through the SATA storage unit performing different operations, it is possible to indicate the use state of the SATA external storage device.