A control device (30a, 30b) configured to be used in a safety protection system of a nuclear power plant, comprising: two arithmetic units (32a, 32b) respectively configured to execute a same arithmetic processing in parallel and independently, based on a detection result of a detection unit (10a, 10b, 10c, 10d) for detecting a specific event occurring in the nuclear power plant, and to each output a control signal to control countermeasure unit (40a, 40b) for taking countermeasures against the event in accordance with an arithmetic result of the arithmetic processing; a transmission unit configured to send out the control signal to the countermeasure unit (40a, 40b), when the control signal is outputted from one of the two arithmetic units (32a, 32b); and a control unit configured to perform control so as to not output the control signal from the one arithmetic unit as a test object from being sent out from the transmission unit while maintaining a state where the other arithmetic unit executes the arithmetic processing independently, when a test of the one arithmetic unit (32a, 32b) is conducted, characterized in that the two arithmetic units (32a, 32b) are configured so that their arithmetic cycles are shifted from each other by a magnitude shorter than the execution cycle of the command, and the control unit is configured to perform a matching process by transcribing a data stored in a storage device of the other arithmetic unit to a storage device of the one arithmetic unit and transcribing a value of a command pointer indicating a command being executed by the other arithmetic unit to a command pointer of the one arithmetic unit, when the test of the one arithmetic unit is completed. two arithmetic units (32a, 32b) respectively configured to execute a same arithmetic processing in parallel and independently, based on a detection result of a detection unit (10a, 10b, 10c, 10d) for detecting a specific event occurring in the nuclear power plant, and to each output a control signal to control countermeasure unit (40a, 40b) for taking countermeasures against the event in accordance with an arithmetic result of the arithmetic processing; a transmission unit configured to send out the control signal to the countermeasure unit (40a, 40b), when the control signal is outputted from one of the two arithmetic units (32a, 32b); and a control unit configured to perform control so as to not output the control signal from the one arithmetic unit as a test object from being sent out from the transmission unit while maintaining a state where the other arithmetic unit executes the arithmetic processing independently, when a test of the one arithmetic unit (32a, 32b) is conducted, characterized in that the two arithmetic units (32a, 32b) are configured so that their arithmetic cycles are shifted from each other by a magnitude shorter than the execution cycle of the command, and the control unit is configured to perform a matching process by transcribing a data stored in a storage device of the other arithmetic unit to a storage device of the one arithmetic unit and transcribing a value of a command pointer indicating a command being executed by the other arithmetic unit to a command pointer of the one arithmetic unit, when the test of the one arithmetic unit is completed.