The number of lower limb disabled people has lately been increasing because of traffic accidents and aged society. Most of the lower limb disabled people live daily on wheelchairs. Stairs and steps are considerable obstacles for the people whose living depends upon wheelchairs. Although stair climbable robots have been developed for extreme tasks, they are of large size, heavy weight, and are too forcefull for stairs at home or hospitals. Therefore they are not suitable for welfare purpose at home or hospital. This study aims at the development of stair climbing wheelchair (S.C.W) which offer assistance for the lower limb disabled people. This report describes the legs mechanism of the S.C.W principle for stair climbing and descending movements, and the design of S.C.W prototype