A wireless LAN access authentication system capable of shortening the time required for an access authentication procedure of a radio terminal apparatus. In this wireless LAN access authentication system, when a radio terminal apparatus 116 of a user who has sent an access request is already registered through initial access, a gateway apparatus 111 searches for a WEP key assigned to the radio terminal apparatus 116 through a WEP key control section 306 and redistributes the WEP key registered beforehand to a new access point section 124 in the destination area and the radio terminal apparatus 116. The radio terminal apparatus 116 and access point section 124 to which the WEP key has been distributed encrypt transmission/reception data in a predetermined radio section using the redistributed WEP key and carry out a communication.