Abstract: A processing machine processes a work and repeats processes on the work, thereby consuming energy. Within the consumed energy, room for improvement is computed by an energy monitoring device and is referred to as an amount of energy that can be improved. An energy monitoring device includes a power data acquirer that acquires a time-series power data measured by a power meter, a cycle detector that detects a single-cycle power data from the power data acquired by the acquirer, a divider that divides the single-cycle power data detected by the detector into an added-value creating portion and an unproductive portion, and a computing unit that computes an amount of energy consumed in the unproductive portion divided by the divider and defines it as the amount of energy to be improved.