An anomaly diagnosis device diagnoses anomaly of an oil-hydraulic operating mechanism that controls opening and closing of a circuit breaker. The anomaly diagnosis device includes: a first counter, which is a counter that counts the number of times of a pressure-increasing operation started upon a decrease in a hydraulic pressure maintained in the oil-hydraulic operating mechanism to a first reference pressure, and stopped upon an increase in the hydraulic pressure to a second reference pressure; a timer that measures an operation interval that is a time period from when a pressure-increasing operation is stopped until a next pressure-increasing operation is started; and an anomaly determiner that corrects, based on the operation interval, the number of pressure-increasing operations obtained based on a result of counting by the counter, and determines presence or absence of an anomaly in the oil-hydraulic operating mechanism using the corrected data of the number of pressure-increasing operations.