Abstract: A load monitoring apparatus has a structure that the electric-power value of a motor is sampled in response to a sampling signal, the sampling cycle of which is changed at a predetermined recursive number. Moreover, the electric-power value is calculated in accordance with a result of the sampling is subjected to an absolute-value range and a relative-value range which is determined in accordance with the previously calculated electric-power value so as to determine an abnormal load of the motor. The sampling cycle is elongated in predetermined steps to correspond to the characteristic of, for example, a reduction gear until a stable driving state is obtained so that an abnormal state of the load such that the load is gradually increased or decreased is detected in accordance with the relative-value range before the abnormal state exceeds limits of the absolute-value range.