A semiconductor device comprising: a process execution unit comprising a plurality of processors and configured such that an operating condition thereof including a combination of number of processors to operate and operating frequency of the number of processors to operate can be varied; and an operation control unit comprising a power source control unit and a clock control unit and configured to determine a number of processors to operate and an operating frequency of the number of processors to operate, by referring to a performance table representing a relationship between operating condition and processing capacity of the process execution unit and a power consumption table representing a relationship between operating condition and power consumption, wherein: the power source control unit is configured to supply electricity to the determined number of processors to operate and cut off power supply to remaining processor(s) that are not to be operated, the clock control unit is configured to supply clock signals of the determined operating frequency to the processors to operate, the power consumption related to the operation condition in the power consumption table includes a leak power depending on a temperature, the operation control unit is configured to extract one or more operating conditions associated with a processing capacity having a predetermined relationship with respect to a reference processing capacity referring to the performance table, when one operating condition is extracted, the operation control unit is configured to control the operating condition of the process execution unit to be the one operating condition extracted, and when a plurality of operating conditions are extracted, the operation control unit is configured to identify, referring to the power consumption table, an operating condition with the lowest power consumption among the plurality of operating conditions, and control the operating condition of the process execution unit to be the operating condition identified. a process execution unit comprising a plurality of processors and configured such that an operating condition thereof including a combination of number of processors to operate and operating frequency of the number of processors to operate can be varied; and an operation control unit comprising a power source control unit and a clock control unit and configured to determine a number of processors to operate and an operating frequency of the number of processors to operate, by referring to a performance table representing a relationship between operating condition and processing capacity of the process execution unit and a power consumption table representing a relationship between operating condition and power consumption, wherein: the power source control unit is configured to supply electricity to the determined number of processors to operate and cut off power supply to remaining processor(s) that are not to be operated, the clock control unit is configured to supply clock signals of the determined operating frequency to the processors to operate, the power consumption related to the operation condition in the power consumption table includes a leak power depending on a temperature, the operation control unit is configured to extract one or more operating conditions associated with a processing capacity having a predetermined relationship with respect to a reference processing capacity referring to the performance table, when one operating condition is extracted, the operation control unit is configured to control the operating condition of the process execution unit to be the one operating condition extracted, and when a plurality of operating conditions are extracted, the operation control unit is configured to identify, referring to the power consumption table, an operating condition with the lowest power consumption among the plurality of operating conditions, and control the operating condition of the process execution unit to be the operating condition identified. the power source control unit is configured to supply electricity to the determined number of processors to operate and cut off power supply to remaining processor(s) that are not to be operated, the clock control unit is configured to supply clock signals of the determined operating frequency to the processors to operate, the power consumption related to the operation condition in the power consumption table includes a leak power depending on a temperature, the operation control unit is configured to extract one or more operating conditions associated with a processing capacity having a predetermined relationship with respect to a reference processing capacity referring to the performance table, when one operating condition is extracted, the operation control unit is configured to control the operating condition of the process execution unit to be the one operating condition extracted, and when a plurality of operating conditions are extracted, the operation control unit is configured to identify, referring to the power consumption table, an operating condition with the lowest power consumption among the plurality of operating conditions, and control the operating condition of the process execution unit to be the operating condition identified.