The present invention provides a processor that cyclically executes a plurality of threads in accordance with an execution time allocated to each of the threads, comprising a reconfigurable integrated circuit. The processor stores circuit configuration information sets respectively corresponding to the plurality of threads, reconfigures a part of the integrated circuit based on the circuit configuration information sets, and sequentially executes each thread using the integrated circuit that has been reconfigured based on one of the configuration information sets that corresponds to the thread. While executing a given thread, the processor selects a thread to be executed next, and reconfigures a part of the integrated circuit where is not currently used for execution of the given thread, based on a circuit configuration information set corresponding to the selected thread.