To enable many radio terminals to make data communication simulta neously by assigning a data communication resource efficiently into plural radio base stations.

A radio base station A3 is provided with a means 4 that makes data communication with plural radio terminals A1, B2, a means 7 that checks the idle state of a data communication resource, a means 8 that acquires the data communication resource, a means 5 that connects a data link, a means 10 that holds a radio terminal possible to hand-over to another radio base station, a means 11 that detects the radio terminal possible to hand-over to the other radio base station and a means 12 that requests hand-over to the radio terminal and the resource is efficiently assigned to the plural radio base stations.