A processing device, adapted for simulating a control system having a control object comprising a motor and a motor control device controlling the motor, thereby determining a device control parameter set in the motor control device, wherein the processing device comprises: a simulation system, comprising a predetermined feedback system having, as forward elements, a model control unit obtained by modeling one or more controllers comprised in the motor control device and a predetermined control block structure corresponding to a predetermined device-side configuration comprising the control object; a holding unit, holding impulse response information for calculation which is information on an impulse response relating to the predetermined device-side configuration; a first response calculation unit, calculating a time response of the predetermined device-side configuration to a predetermined input value by convolution processing using the impulse response information for calculation and the predetermined input value; a second response calculation unit, calculating a response of the simulation system to a command value input to the simulation system by using the time response of the predetermined device-side configuration calculated by the first response calculation unit; a performance index calculation unit, changing a model control parameter set in the model control unit and performing the calculations in the first response calculation unit and the second response calculation unit, thereby calculating a correlation between a predetermined performance index representing a control characteristic of the control object by the motor control device and the model control parameter based on a response result of the simulation system; and a parameter determination unit, determining the device control parameter based on the correlation calculated by the performance index calculation unit. a simulation system, comprising a predetermined feedback system having, as forward elements, a model control unit obtained by modeling one or more controllers comprised in the motor control device and a predetermined control block structure corresponding to a predetermined device-side configuration comprising the control object; a holding unit, holding impulse response information for calculation which is information on an impulse response relating to the predetermined device-side configuration; a first response calculation unit, calculating a time response of the predetermined device-side configuration to a predetermined input value by convolution processing using the impulse response information for calculation and the predetermined input value; a second response calculation unit, calculating a response of the simulation system to a command value input to the simulation system by using the time response of the predetermined device-side configuration calculated by the first response calculation unit; a performance index calculation unit, changing a model control parameter set in the model control unit and performing the calculations in the first response calculation unit and the second response calculation unit, thereby calculating a correlation between a predetermined performance index representing a control characteristic of the control object by the motor control device and the model control parameter based on a response result of the simulation system; and a parameter determination unit, determining the device control parameter based on the correlation calculated by the performance index calculation unit.