Motor controller and motor control system

A motor control system (200) includes a motor (1) connected to a load (2) through a connecting shaft (3), an electric power converter (4) for driving the motor, and a motor controller (100) for controlling the electric power converter according to a target command value and a motor current that flows in the motor; the motor controller has an auto tuner (11) that receives a motor torque value and motor rotational speed of the motor as input signals and automatically adjusts control parameters used in the control; the auto tuner handles a machine system including the motor, connecting shaft, and load as a rigid-body model and a resonant model that are connected in series, the auto tuner having a parameter identifying means for separately identifying parameters constituting the rigid-body model and parameters constituting the resonant model. Both rigid-body characteristics and resonant characteristics of a controlled target can thereby be identified online with a small amount of calculation.