Load state diagnosis device and load state diagnosis method for servomotor

A load state diagnosis device for a servomotor which diagnoses a load state of the servomotor rotationally driving a rotary tool in a predetermined rotational drive direction at a constant speed, comprising:

• a detection part that detects a rotational direction of a torque acting on the servomotor;
• a determination part that determines whether or not the rotational direction of the torque detected by the detection part is consistent with the predetermined rotational drive direction;
• and
• a load index output part that outputs a load index indicating the load state of the servomotor based on a determination result of the determination part, wherein the load index output part calculates an integrated value of a period of a state in which the rotational direction of the torque is inconsistent with the predetermined rotational drive direction and outputs the load index based on the integrated value.