Gait-training robots are used to improve gait performance by assisting motion. A robotic assistance method to encourage people to learn an induced gait is required, and robotic control methods of assistance as needed to enhance the active participation of patients have been studied. In this paper, we propose an intermittent force control method with a wire-driven gait-training robot to encourage people to learn the induced gait. We focused on a force-assisting knee flexion with increased toe clearance. We used an assistance timing detection method for the robot, conducting tensile force control based on information from the hip, knee, and ankle angles. The gait-training robot controlled the wire tensile force by controlling the motor rotation, and could switch between a mode in which force was applied and a mode in which force was not applied. We investigated the effect of the frequency of force application on the change in knee flexion angle after the gait-training robot stopped intervention. We confirmed that intermittent force application that did not assist every gait cycle was more beneficial in encouraging people to learn the induced gait than force application during every gait cycle.