More than one million people have difficulty in walking at least only in Japan. Many kinds of walker have been developing so far for gait training though, they are used by grasping the front and/or the back part of them in order to hold trunk. It makes forward tilting or backward tilting of the upper half of the body and comes to difficult to keep right posture for walking. Moreover there are few examples of an active walker which is used if people have no muscular force for walking. In order to solve these issues, we have been developing the active walker by using the Hart Walker (HW) which consists of double upright knee ankle foot orthosis and 4-wheeled carriage with a stem located in the center of the carriage. Since waist part of the orthosis is attached to the top of the stem, there is no risk for falling, it is possible to keep the right posture, and both hands becomes completely be free. McKibben artificial muscles are attached to HW in order to control gait as an active walker. By walking experiment using child-size doll with the same kind of joints human has and weight, it is confirmed that human-like gait is realized by the active walker developed. Now the active walker is test working stage. Many subjects who have different kinds of disease are trying to use it and we have confirmed all of them can walk by using the active walker.