A radio base station according to an embodiment constitutes a mobile communication network. The radio base station comprises: a controller configured to measure a stay time for which a radio terminal has stayed on a wireless LAN. The stay time is a period from when a first process through which the radio terminal switches a waiting destination or a connection destination from the mobile communication network to the wireless LAN is performed to when a second process through which the radio terminal switches the waiting destination or the connection destination from the wireless LAN to the mobile communication network is performed.