A mobile communication method according to the present invention includes a step of monitoring, by a radio base station 201 connected to a user network, certain traffic in the user network, step of notifying, by the radio base station 201, a mobile communication network of communication quality information indicating that communication quality therein is not assurable when the radio base station 201 detects that the certain traffic exceeds a predetermined threshold, step of transmitting, by a mobile station 300, a communication start request which requests start of specific communication, to the mobile communication network, step of selecting, by the mobile communication network upon receipt of the communication start request, a radio base station to which the mobile station is connected at the time of performing the specific communication, the selection being made on the basis of the communication quality information, and step of starting, by the mobile station 300, the specific communication through the selected radio base station.