Embodiments of the present invention disclose a method and an apparatus for monitoring a network device, and relate to the field of information network technologies. The method in the present invention includes acquiring basic service set identifiers (BSSIDs) of wireless network devices in a network system managed by a network management system and determining BSSIDs of unauthorized wireless network devices in the acquired BSSIDs of the wireless network devices in the network system by using a fingerprint database of authorized wireless network devices. The method also includes acquiring a media access control (MAC) forwarding table corresponding to a network port used by a user and determining an unauthorized wireless network device connected to the network port according to the BSSIDs of the unauthorized wireless network devices and a MAC address.