PROBLEM TO BE SOLVED: To provide a muscle activity monitoring device and a muscle activity monitoring program that can monitor a muscle activity of a portion to be inspected without preliminarily measuring the maximum muscular strength of the portion to be inspected and can monitor a state of the muscle activity by classifying it more finely.SOLUTION: A muscle activity monitoring device comprises: a storage part that stores determination information for determining a state of a muscle activity an acquisition control part that acquires integrated myoelectric values Y at a portion to be inspected and a determination control part. The determination control part executes: an average value and a coefficient of variation calculation processing S56 and S57 of calculating an average value of the integrated myoelectric values Y at the portion to be inspected and a coefficient of variation C.V thereof, on the basis of the integrated myoelectric value Y and continuing muscle activity determination processing S59 of determining whether the muscle activity continues at the portion to be inspected, on the basis of the calculated average value and coefficient of variation C.V of the integrated myoelectric values Y and also on the basis of the average value and coefficient of variation C.V of the integrated myoelectric values Y that are stored in the storage part as the determination information.
