PROBLEM TO BE SOLVED: To provide a periodic disturbance suppression device capable of correcting a system identification model error. SOLUTION: The periodic disturbance suppression device includes: a periodic disturbance observer PDO which has a controller for generating a control command value rnin a higher order, estimates periodic disturbance by multiplying an inverse system expressed by an inverse number of a system identification model, at an output yn of a control target plant Pngenerated by the periodic disturbance, with a frequency component of the periodic disturbance as a suppression control target, and subtracting it from the rnto suppress a periodic disturbance dn; phase calculation means (10, 11) for calculating a phase errorθrefby the system identification model error on the basis of a vector track drawn on a complex vector plane by respective frequency components of the periodic disturbance during periodic disturb
