A plant assistance assessment system for acquiring plant data from a plurality of plants via a network providing a communication between each of the plants and a plant assistance facility provided at a location different from a location of the plants, the plant assistance assessment system being configured to assess the plants based on the plant data, and the plant assistance assessment system being provided in the plant assistance facility, the plant assistance assessment system comprising: an abnormality sign monitoring system configured to monitor an abnormality sign in each plant based on the plant data; a fault diagnosis system configured to perform fault diagnosis on each of devices provided in each plant and configured to specify a device causing an abnormality based on abnormality sign detection information that is information on an abnormality sign detected by the abnormality sign monitoring system; a progress prediction system configured to simulate progress of each plant, based on fault information that is information on a fault in the device specified by the fault diagnosis system, and configured to predict the progress of each plant; an abnormal phenomenon specification system configured to specify a potential abnormal phenomenon in each plant, based on progress prediction information that is information on the progress of each plant predicted by the progress prediction system; a risk assessment system configured to acquire the fault information from the fault diagnosis system, and to assess a risk of a fault in each of devices provided in each plant in a probabilistic manner; and an abnormal phenomenon assessment system configured to assess likelihood of occurrence of an abnormal phenomenon, based on abnormal phenomenon information that is information on the abnormal phenomenon specified by the abnormal phenomenon specification system, and fault probability information that is information on fault probability of the devices assessed by the risk assessment system, wherein the risk assessment system is configured to re-assess the risk of a fault and to update the fault probability information, and the risk assessment system includes a list of devices important to safety for each plant and the risk assessment system is configured to select a device corresponding to the fault information from the list of devices, and to re-assess the risk of a fault in the selected device. an abnormality sign monitoring system configured to monitor an abnormality sign in each plant based on the plant data; a fault diagnosis system configured to perform fault diagnosis on each of devices provided in each plant and configured to specify a device causing an abnormality based on abnormality sign detection information that is information on an abnormality sign detected by the abnormality sign monitoring system; a progress prediction system configured to simulate progress of each plant, based on fault information that is information on a fault in the device specified by the fault diagnosis system, and configured to predict the progress of each plant; an abnormal phenomenon specification system configured to specify a potential abnormal phenomenon in each plant, based on progress prediction information that is information on the progress of each plant predicted by the progress prediction system; a risk assessment system configured to acquire the fault information from the fault diagnosis system, and to assess a risk of a fault in each of devices provided in each plant in a probabilistic manner; and an abnormal phenomenon assessment system configured to assess likelihood of occurrence of an abnormal phenomenon, based on abnormal phenomenon information that is information on the abnormal phenomenon specified by the abnormal phenomenon specification system, and fault probability information that is information on fault probability of the devices assessed by the risk assessment system, wherein the risk assessment system is configured to re-assess the risk of a fault and to update the fault probability information, and the risk assessment system includes a list of devices important to safety for each plant and the risk assessment system is configured to select a device corresponding to the fault information from the list of devices, and to re-assess the risk of a fault in the selected device.