Joint contracture causes a limitation in range of motion (ROM) of the joint. It is hard to treat the contractures of joints. In addition, ROM limitation has an adverse effect on activities of daily living. Therefore, physiotherapists provide ROM exercise to patients for the preventing contracture and improving ROM. However, it is expected that the number of patients who can receive sufficient ROM exercise will decrease due to the declining birthrate and aging population. Therefore, mechanical devices that automatically provide ROM exercise have been developed. Among them, ROM exercise devices for the ankle joints have been actively developed. However, conventional one can only provide plantarflexion and dorsiflexion exercise, and cannot provide pronation and supination exercise. Therefore, in this research, we are developing a novel ROM exercise device for the ankle joints. This device exercises the ankle joints by directly pushing the foot with developed pneumatic soft actuators.