Abstract: A machine diagnosing system is provided which can make an abnormality/failure diagnosis of a machine without using threshold values. It is composed of a dynamic state management controller that creates frequency distribution information showing a relationship between signal intensity related to engine output and occurrence frequency whenever the machine body is operated for a predetermined time, a management section that receives and stores pieces of frequency distribution information, and terminal equipment and each of which detects a decrease in engine output by arranging the pieces of frequency distribution information obtained from the management section in time series and by comparing these pieces of information with each other.