A method and a system of detecting a duplicate service set identifier (SSID) via self-scanning in a WLAN are provided. An access point (AP), when a scan request is given, generates a probe request packet by inserting a SSID of the AP thereinto, transmits the probe request packet to neighbor APs, receives probe response packets, in response to the probe request packet, from the neighbor APs, detects SSIDs from the probe response packets, and informs the presence of a neighbor AP, the SSID of which is the same as that of the AP, if any of the detected SSIDs is the same as the SSID of the AP.