A base station that communicates with a plurality of user terminals in a mobile communication system in which a radio signal including a reference signal for estimating a channel characteristic is transmitted and received, comprises: a control unit that changes a reference signal density that is a density of the reference signal applied to communication with the plurality of user terminals. The control unit calculates a statistics amount of communication quality information acquired for all the plurality of user terminals, and changes the reference signal density on the basis of the statistics amount.