Industrial plant monitoring device, industrial plant monitoring method, and program

A plant monitoring device (20) is provided with: a detection value acquisition unit (211) that acquires a bundle of detection values; a first Mahalanobis distance calculation unit (212) that calculates a first Mahalanobis distance by using as a reference a unit space generated on the basis of a bundle of past detection values; a first SN ratio calculation unit (214) that calculates a first SN ratio for each of a plurality of evaluation items; a second Mahalanobis distance calculation unit (215) that calculates a second Mahalanobis distance by increasing or decreasing each of the detection values; a second SN ratio acquisition unit (216) that converts the first SN ratio for each of the evaluation items and acquires a second SN ratio on the basis of the first and second Mahalanobis distances; and an addition unit (217) that calculates an added value of a plurality of the second SN ratios acquired within a prescribed period for each of the evaluation items.