A network selection control method according to a first aspect is a method of controlling a network selection operation for selecting an access network in which traffic of a user terminal is exchanged from among a cellular RAN and a wireless LAN. The network selection control method comprises: a step A of transmitting, by the cellular RAN, RAN assistance information utilized for the network selection operation; a step B of receiving, by the user terminal, the RAN assistance information; and a step C of performing, by the user terminal, the network selection operation based on the RAN assistance information. The RAN assistance information includes predetermined information for determining whether or not the selection of the wireless LAN is permitted. The predetermined information is associated with a load status of the cellular RAN.