A power consumption controller controls the power consumption of a physical server having a virtual server. A management server determines an unused CPU budget from the difference between the total amount of the loads of respective virtual servers and a hypervisor and the total CPU budget of the physical server. The management server determines the drive frequency of the CPU inside the physical server based on the unused CPU budget. The management server changes a CPU allocation budget related to the respective virtual servers and the hypervisor in accordance with the determined drive frequency. The hypervisor controls the CPU allocation budget and drive frequency in accordance with an indication from the management server.Accordingly, the power consumption of the physical server is controlled.