The present invention relates to a method for searching and releasing an abnormal subscriber station in a wireless portable Internet system, and an apparatus using the same. The apparatus searches for an abnormal group including abnormal subscriber stations based on a ranging code provided in a periodic ranging process, and searches for an abnormal subscriber station by transmitting a connection maintenance message to subscriber stations included in the abnormal group so as to check an operation status of the respective subscriber stations. In addition, the apparatus releases a connection of an abnormal subscriber station. Therefore, waste of radio resources allocated to the abnormal subscriber station can be prevented, thereby achieving efficient resource management. Further, a secondary search process is performed only for subscriber stations included in an abnormal group, thereby preventing a system load from occurring when searching for an abnormal subscriber station.