Intended is to provide a manipulation simulator, which performs, even if a reaction generating spring has linear spring characteristics, preferred continuous nonlinear characteristics as a relation between a manipulated variable and a manipulation reaction all over the manipulations on manipulation means. The manipulation simulator comprises an input member for performing motions in response to abraking manipulation of the driver on a brake pedal, a reaction generating device for generating a reaction in accordance with a quantity of deformation, an output member for deforming the reaction generating device, and a transmission device interposed between the input member and the output member for transmitting the motion of the input member to the output member so that the reaction of the reaction generating device may be transmitted through the output member to the input member. The motion of the input member is a linear motion. The reaction generating device generates a reaction linearly according to the quantity of deformation, and converts the linear motion of the input member into the rotary motion thereby to transmit the rotary motion to the output member, so that it changes the ratio of the momentum of the output member to the momentum of the input member, continuously nonlinearly according to the momentum of the input member.