A plant maintenance assisting system comprising: an abnormality indication monitoring system that is configured to detect an abnormality indication of a nuclear power plant; an abnormality diagnosis system that is configured to specify an abnormal event of the nuclear power plant on the basis of a result of the detection of the abnormality indication, the plant maintenance assisting system characterised in that the abnormality diagnosis system is further configured to specify an abnormality indicating facility associated with the specified abnormal event, and to generate abnormality diagnosis information including information relating to the abnormal event and the abnormality indicating facility which are specified; the plant maintenance assisting system further comprising a maintenance plan creation system that is configured to create a maintenance plan of the nuclear power plant; a risk evaluation system that is configured to evaluate risk occurring in the nuclear power plant due to standby exception of a facility including the abnormality indicating facility, and to generate risk information as a result of the evaluation; and a component management system that has component management information for managing a component used in the nuclear power plant, wherein the risk evaluation system is configured to determine a need for maintenance work with respect to the abnormality indicating facility on the basis of the risk information and the abnormality diagnosis information, wherein in a case where it is determined that the maintenance work with respect to the abnormality indicating facility is necessary, the maintenance plan creation system is configured to set maintenance implementation timing of maintenance work with respect to the facility including the abnormality indicating facility, in the maintenance plan, and wherein the component management system is configured to determine whether the component is able to be procured on the basis of the component management information, at the maintenance implementation timing which is set by the maintenance plan creation system. an abnormality indication monitoring system that is configured to detect an abnormality indication of a nuclear power plant; an abnormality diagnosis system that is configured to specify an abnormal event of the nuclear power plant on the basis of a result of the detection of the abnormality indication, the plant maintenance assisting system characterised in that the abnormality diagnosis system is further configured to specify an abnormality indicating facility associated with the specified abnormal event, and to generate abnormality diagnosis information including information relating to the abnormal event and the abnormality indicating facility which are specified; the plant maintenance assisting system further comprising a maintenance plan creation system that is configured to create a maintenance plan of the nuclear power plant; a risk evaluation system that is configured to evaluate risk occurring in the nuclear power plant due to standby exception of a facility including the abnormality indicating facility, and to generate risk information as a result of the evaluation; and a component management system that has component management information for managing a component used in the nuclear power plant, wherein the risk evaluation system is configured to determine a need for maintenance work with respect to the abnormality indicating facility on the basis of the risk information and the abnormality diagnosis information, wherein in a case where it is determined that the maintenance work with respect to the abnormality indicating facility is necessary, the maintenance plan creation system is configured to set maintenance implementation timing of maintenance work with respect to the facility including the abnormality indicating facility, in the maintenance plan, and wherein the component management system is configured to determine whether the component is able to be procured on the basis of the component management information, at the maintenance implementation timing which is set by the maintenance plan creation system.