There is provided a method for controlling a transmission power in a second communication service making secondary usage of a spectrum assigned to a first communication service, with use of any node of one or more secondary usage node that transmits a radio signal of the second communication service, comprising the steps of: acquiring an acceptable interference power allocated to the second communication service; calculating a total sum of interference power levels on the first communication service based on transmission powers respectively required for the one or more secondary usage node; and excluding any secondary usage node of the one or more secondary usage node from allocation of the transmission power when the calculated total sum of interference power levels is larger than the acceptable interference power.