A network device, a network connection detector and a detection method thereof are disclosed. The network device comprises a socket, a waveform generator and a reflected wave detector. The waveform generator sends a first test wave to at least a first contact of a plurality of contacts of a socket and then the reflected wave detector detects a first reflected wave that is corresponding to the first test wave and is reflected from the first contact. Thus a first control signal is generated according to detection result of the first reflected wave.