A control system for a nuclear facility comprising: a detecting sensor for the nuclear facility, being configured to output an abnormality detecting signal at the time of occurrence of an abnormality in the nuclear facility; a main control device including a digital facility configured to execute software to output a normal operation signal when a unit is operated normally in consequence of controlling the unit provided in the nuclear facility on the safe side based on the abnormality detecting signal; and an auxiliary control device, as an auxiliary of the main control device, including an analog device configured to output an auxiliary operation signal to operate the unit on the safe side in a case where the auxiliary control device determines from output results of the abnormality detecting signal and the normal operation signal that the unit is not operated normally for the abnormality in the nuclear facility, wherein the auxiliary control device includes: a NOT circuit (76, 86, 98) connected to an output side of the main control device, and configured to invert input or no input of the normal operation signal and output an inverted signal; a first AND circuit (75, 85, 100) configured to output the auxiliary operation signal based on input or no input of the signal output from the NOT circuit (76, 86, 98) and input or no input of the abnormality detecting signal, and a delay circuit (74, 84, 96), wherein the detecting sensor is connected to an input side of the first AND circuit (75, 85, 100) via the delay circuit (74, 84, 96) and the digital main control device is connected to another input side of the first AND circuit (75, 85, 100) via the NOT circuit (76, 86, 98). a detecting sensor for the nuclear facility, being configured to output an abnormality detecting signal at the time of occurrence of an abnormality in the nuclear facility; a main control device including a digital facility configured to execute software to output a normal operation signal when a unit is operated normally in consequence of controlling the unit provided in the nuclear facility on the safe side based on the abnormality detecting signal; and an auxiliary control device, as an auxiliary of the main control device, including an analog device configured to output an auxiliary operation signal to operate the unit on the safe side in a case where the auxiliary control device determines from output results of the abnormality detecting signal and the normal operation signal that the unit is not operated normally for the abnormality in the nuclear facility, wherein the auxiliary control device includes: a NOT circuit (76, 86, 98) connected to an output side of the main control device, and configured to invert input or no input of the normal operation signal and output an inverted signal; a first AND circuit (75, 85, 100) configured to output the auxiliary operation signal based on input or no input of the signal output from the NOT circuit (76, 86, 98) and input or no input of the abnormality detecting signal, and a delay circuit (74, 84, 96), wherein the detecting sensor is connected to an input side of the first AND circuit (75, 85, 100) via the delay circuit (74, 84, 96) and the digital main control device is connected to another input side of the first AND circuit (75, 85, 100) via the NOT circuit (76, 86, 98). a NOT circuit (76, 86, 98) connected to an output side of the main control device, and configured to invert input or no input of the normal operation signal and output an inverted signal; a first AND circuit (75, 85, 100) configured to output the auxiliary operation signal based on input or no input of the signal output from the NOT circuit (76, 86, 98) and input or no input of the abnormality detecting signal, and a delay circuit (74, 84, 96), wherein the detecting sensor is connected to an input side of the first AND circuit (75, 85, 100) via the delay circuit (74, 84, 96) and the digital main control device is connected to another input side of the first AND circuit (75, 85, 100) via the NOT circuit (76, 86, 98).