To provide a motor controller that uses input values of machine parameters and operation parameters for motor control parameter calculation.

The motor controller includes a motor specification data storage unit which stores motor specification data of a motor, a machine parameter input unit which sets machine data comprising types of machine elements that the motor drives and characteristic values of the respective machine elements, an operation parameter input unit which inputs a speed command pattern of operation, a data storage unit which stores the machine data and a speed command pattern, a machine characteristic analysis unit which analyzes response data of the motor received from the motor controller to generate resonance and antiresonance frequencies, a control parameter calculation unit which calculates motor control parameters from resonance and antiresonance frequencies, a capacity selection calculation unit which calculates the capacity of a machine from motor specification data, the speed command pattern, and characteristic values of the machine elements, and a capacity selection calculation result storage unit which stores the capacity selection calculation result.