Provided is a monitoring apparatus including an acquisition unit that acquires first time-series data which is time-series data of a measured value and/or a feature amount regarding an electrical device group, and a registration and updating unit that, when a difference in values between a pre-state-change data value which is any one of a data value at a first point in time in the first time-series data and a statistic of a plurality of data values from a point in time earlier than the first point in time by a predetermined period of time to the first point in time and a post-state-change data value which is any one of a data value at a second point in time later than the first point in time and a statistic of a plurality of data values from the second point in time to a point in time later than the second point in time by a predetermined period of time satisfies a predetermined condition, stores a feature amount extracted from any waveform data of a total current consumption, a total power consumption, and a total input voltage of the electrical device group corresponding to the pre-state-change data value and the post-state-change data value which satisfy the predetermined condition, in a feature amount storage unit.