An abnormality detecting system and an abnormality detecting method acquires a stroke of a piston as input from outside, calculates a travel time of the piston based on the results of sensing obtained by a first sensor and a second sensor, calculates a total travel distance of the piston using the number of operations and the stroke of the piston, and detects an abnormality of the actuator based on the travel time and the number of operations or the total travel distance of the piston.