A monitoring system, comprising: an operation results acquisition unit adapted to acquire time series data of each of a plurality of indexes which are an availability rate, performance rate and quality rate that indicate operation results of a production equipment; an overall index generation unit adapted to produce time series data of an overall equipment effectiveness by combining index values by availability rate x performance rate x quality rate at a same time point based on the time series data of each of the plurality of indexes, wherein the availability rate = operating time / planned production time, the performance rate = net operating time / planned production time, and the quality rate = good pieces / total pieces produced during a unit period, where planned production time = unit period − planned downtime during the unit period, operating time = planned production time − unplanned downtime during the unit period, wherein unplanned downtime refers wherein unplanned downtime refers to a stop due to an abnormality in the production equipment and involves a long-time stop for determination of causes, repair, replacement, during the unit period, wherein minor downtime refers to a stop wherein minor downtime refers to a stop during normal operation of the production equipment for simple, short-time measures such as removal of work piece or resetting to be taken before a restart, and good pieces = total pieces − reject pieces produced during the unit period; and a change point detection unit adapted to analyze the time series data of the overall equipment effectiveness, and to detect a point where a significant change appears in values of the overall equipment effectiveness, as a change point in a status of the production equipment; the monitoring system further comprising a cause analysis unit adapted to analyze the time series data of the plurality of indexes and the time series data of the overall equipment effectiveness when a change point is detected in the status of the production equipment by the change point detection unit, and to select, from the plurality of indexes, one or more indexes with a high level of contribution to the change in the overall index at the change point as a notable index relevant to a cause of the change in the status of the production equipment, and a storage unit adapted to store a causal event table in which types of the indexes, variation trends, and causal events are corresponded to one another, wherein the cause analysis unit is adapted to analyze a variation trend of the time series data of the notable index, and to specify a causal event assumed to be the cause of the change in the status of the production equipment by acquiring from the causal event table a causal event corresponding to the notable index and to the analysed variation trend. an operation results acquisition unit adapted to acquire time series data of each of a plurality of indexes which are an availability rate, performance rate and quality rate that indicate operation results of a production equipment; an overall index generation unit adapted to produce time series data of an overall equipment effectiveness by combining index values by availability rate x performance rate x quality rate at a same time point based on the time series data of each of the plurality of indexes, wherein the availability rate = operating time / planned production time, the performance rate = net operating time / planned production time, and the quality rate = good pieces / total pieces produced during a unit period, where planned production time = unit period − planned downtime during the unit period, operating time = planned production time − unplanned downtime during the unit period, wherein unplanned downtime refers wherein unplanned downtime refers to a stop due to an abnormality in the production equipment and involves a long-time stop for determination of causes, repair, replacement, during the unit period, wherein minor downtime refers to a stop wherein minor downtime refers to a stop during normal operation of the production equipment for simple, short-time measures such as removal of work piece or resetting to be taken before a restart, and good pieces = total pieces − reject pieces produced during the unit period; and a change point detection unit adapted to analyze the time series data of the overall equipment effectiveness, and to detect a point where a significant change appears in values of the overall equipment effectiveness, as a change point in a status of the production equipment; the monitoring system further comprising a cause analysis unit adapted to analyze the time series data of the plurality of indexes and the time series data of the overall equipment effectiveness when a change point is detected in the status of the production equipment by the change point detection unit, and to select, from the plurality of indexes, one or more indexes with a high level of contribution to the change in the overall index at the change point as a notable index relevant to a cause of the change in the status of the production equipment, and a storage unit adapted to store a causal event table in which types of the indexes, variation trends, and causal events are corresponded to one another, wherein the cause analysis unit is adapted to analyze a variation trend of the time series data of the notable index, and to specify a causal event assumed to be the cause of the change in the status of the production equipment by acquiring from the causal event table a causal event corresponding to the notable index and to the analysed variation trend.