An apparatus to control a reaction force of an accelerator includes a detector to detect an opening degree of the accelerator, and a controller to increase the reaction force by a first force magnitude during a period in which the vehicle transitions from a first operational state to a second operational state in response to an increase in the opening degree of the accelerator, wherein the controller increases the reaction force if the accelerator opening degree is increased within a predetermined time period after the reaction force is increased by the first force magnitude, wherein the first operational state corresponds to a low specific fuel consumption and the second operational state corresponds to a high specific fuel consumption, and wherein the controller decreases the reaction force by the first force magnitude in response to a reduction in the opening degree of the accelerator.