A maintenance support system (1, 2) for a process control system, comprising: a first storage unit which stores first specification information including configurations and settings for devices of the process control system which is configured to perform control of an industrial process implemented in a plant, the first specification information being correctable by a system engineer managing the process control system; an actual condition information extraction unit configured to extract, from the process control system actual condition information including configurations and settings of devices of the process control system; and a first comparison unit configured to output first information indicating a result of comparing the first specification information stored in the first storage unit with the actual condition information extracted by the extraction unit; a second storage unit configured to store second specification including configurations and settings for the devices of the process control system; an updating unit configured to update the second storage unit so that contents of correction by the system engineer for the first specification information stored in the first storage unit are reflected in the second storage unit when the first information output from the first comparison unit indicates that there is no difference between the first specification information and the actual condition information after a task of changing the actual condition for the process control system is performed; and a notification unit configured to notify a terminal device of the system engineer of the first information output by the first comparison unit and a second information output by a second comparison unit that is also comprised in the maintenance support system (1, 2), wherein the first comparison unit is configured to include, in the first information, information indicating a time at which a difference was generated between the first specification information and the actual condition information, and information on a place in which the difference was generated when there is the difference between the first specification information and the actual condition information, characterized by the second comparison unit being configured to output the second information indicating a result of comparing the second specification information stored in the second storage unit with the actual condition information extracted by the extraction unit; the second comparison unit being configured to include, in the second information, information indicating a time at which a difference was generated between the second specification information and the actual condition information, and information on a place in which the difference was generated when there is the difference between the second specification information and the actual condition information. a first storage unit which stores first specification information including configurations and settings for devices of the process control system which is configured to perform control of an industrial process implemented in a plant, the first specification information being correctable by a system engineer managing the process control system; an actual condition information extraction unit configured to extract, from the process control system actual condition information including configurations and settings of devices of the process control system; and a first comparison unit configured to output first information indicating a result of comparing the first specification information stored in the first storage unit with the actual condition information extracted by the extraction unit; a second storage unit configured to store second specification including configurations and settings for the devices of the process control system; an updating unit configured to update the second storage unit so that contents of correction by the system engineer for the first specification information stored in the first storage unit are reflected in the second storage unit when the first information output from the first comparison unit indicates that there is no difference between the first specification information and the actual condition information after a task of changing the actual condition for the process control system is performed; and a notification unit configured to notify a terminal device of the system engineer of the first information output by the first comparison unit and a second information output by a second comparison unit that is also comprised in the maintenance support system (1, 2), wherein the first comparison unit is configured to include, in the first information, information indicating a time at which a difference was generated between the first specification information and the actual condition information, and information on a place in which the difference was generated when there is the difference between the first specification information and the actual condition information, characterized by the second comparison unit being configured to output the second information indicating a result of comparing the second specification information stored in the second storage unit with the actual condition information extracted by the extraction unit; the second comparison unit being configured to include, in the second information, information indicating a time at which a difference was generated between the second specification information and the actual condition information, and information on a place in which the difference was generated when there is the difference between the second specification information and the actual condition information.