To provide a wireless base station that can warrant prescribed communication quality for the communication between the wireless base station and a mobile station.

A reception timing detection section 55 in a wireless base station 100 making communication with a mobile station in compliance with the PHS standard measures the time as reception timing, when a UW signal is received on the basis of a start point of a time slot of a TDMA/TDD frame of a signal separated by a signal adjustment section 51 by each mobile station. A control section 80 assigns a communication channel to a time slot where a reception timing difference between a new mobile station and all mobile stations having already been in communication comes to a threshold value or over, when newly assigning a communication channel to the mobile station through space multiplex processing.