A device to detect hot-plugging and hot-unplugging of hard disk and the hard disk type includes a connector and a control circuit. When hot-plugged, the hard disk is coupled to the connector, the control circuit comprises delay circuit and latch circuit. The delay circuit delays a falling edge of the third signal and outputs a delay signal, the latch circuit processes the first and second signals and outputs a logical result as a latch signal. The control circuit determines the connected or disconnected status and type of the hard disk according to the respective levels of the first and second signals, the delay signal, and the latch signal. The delay signal and the latch signal work to correct error of the control circuit in determining connectivity and non-connectivity during a session due to asynchronous changes in signal levels of the first and second signals.