The purpose of this study is to develop a wheelchair which can be operated by a physically disabled person on his/her own in a barrier-free construction as smoothly as in the movement of a non-disabled person. While barrier-free environment can be easily obtained by renovating the building, expansion of the room or corridor width is more difficult because of the fixed arrangement of pillars and walls. When viewed from above, a disabled person's body is broadest at his/her shoulder and is narrower at his/her knees. Because of this, by building a wheelchair that fits in a Reuleaux triangle, it is possible to hold the body outline of the disabled person within the wheelchair, and that allows it to turn around inside a narrow corridor. The following results were obtained by experimenting on the prototype. Omni-wheels on the three corners of the wheelchair's frame, each driven by an independently controllable motor, enabled the wheelchair to move omni-directionally. By using three types of operation modes, the wheelchair became more capable of lateral movement in a narrow room, route change for avoiding an obstacle, and sudden course correction. The minimal width of the corridor where it can turn around was 800mm in turning operation, and 750mm in compound operation.