This paper describes a walk-assist machine for the walk rehabilitation or support of the elderly and persons with walking disabilities. The assist machine is designed to be able to deal with a 50mm bump. The base size of the assist machine is 588mm×575mm, and its weight is 13kg. It consists of two front wheels, two rear wheels activated by DC motors, a seat and a handle frame. In order to measure the force exerted by user's hand, a force sensor is attached at the handle frame. According to the value of the force sensor, the speed of the motors is controlled. Through walk assist experiments using the assist machine, the effectiveness of the mechanism and control system is verified.