A simulation device, adapted for simulating a mechanical system which has a controlled object containing a motor and a motor control device controlling the motor, comprising: a frequency response function computing part, adapted for computing a frequency response function containing characteristics of the controlled object based on a relation between a first command value driving the mechanical system and a measured value of response of the mechanical system driven by the first command value; a simulation system, having a control block structure corresponding to the mechanical system; a parameter setting part, adapted for setting the control parameter changing characteristics of the simulation system; a frequency transfer function setting part, adapted for setting a frequency transfer function computed based on the frequency response function or based on the frequency response function and the control parameter into a frequency transfer function used for the simulation; a second command value generating part, adapted for generating a second command value which is a command value for simulation; a frequency response outputting part, adapted for outputting the frequency response characteristic of the mechanical system based on the frequency transfer function for simulation; characterized by a time response outputting part, adapted for executing time response simulation of the mechanical system relative to the second command value based on the second command value and the frequency transfer function for simulation; a display control part, adapted for displaying a result of the time response simulation and the frequency response characteristic on a display part simultaneously or selectively, and wherein the frequency response outputting part is adapted to output at least one of a gain response characteristic and a phase response characteristic as the frequency response characteristic. a frequency response function computing part, adapted for computing a frequency response function containing characteristics of the controlled object based on a relation between a first command value driving the mechanical system and a measured value of response of the mechanical system driven by the first command value; a simulation system, having a control block structure corresponding to the mechanical system; a parameter setting part, adapted for setting the control parameter changing characteristics of the simulation system; a frequency transfer function setting part, adapted for setting a frequency transfer function computed based on the frequency response function or based on the frequency response function and the control parameter into a frequency transfer function used for the simulation; a second command value generating part, adapted for generating a second command value which is a command value for simulation; a frequency response outputting part, adapted for outputting the frequency response characteristic of the mechanical system based on the frequency transfer function for simulation; characterized by a time response outputting part, adapted for executing time response simulation of the mechanical system relative to the second command value based on the second command value and the frequency transfer function for simulation; a display control part, adapted for displaying a result of the time response simulation and the frequency response characteristic on a display part simultaneously or selectively, and wherein the frequency response outputting part is adapted to output at least one of a gain response characteristic and a phase response characteristic as the frequency response characteristic.