A processor, which cyclically executes a plurality of threads with each thread executed for a respective time assigned thereto, has a reconfigurable integrated circuit. Circuit configuration information corresponding to each of the plurality of threads is stored, and a part of the integrated circuit is reconfigured based on the circuit configuration information. The integrated circuits reconfigured based on the circuit configuration information corresponding to the respective threads are sequentially used to execute the respective threads. While a thread is being executed, a thread to be executed next is selected. A part of the integrated circuit, which is a part other than the part of the integrated circuit that is used for the thread being executed, is reconfigured for the thread to be executed next.