To date, many control methods have been researched on the assumption that the soles of a biped walking robot contact the ground as four points. It is difficult for almost all biped robots to maintain four-point-contact on uneven terrain because they have rigid and flat soles. It means that the biped robots can lose their balance. To solve this kind of problem, not only stability controls but also foot mechanisms should be studied. So, we developed a foot system, WS-1 (Waseda Shoes - No.1) that can maintain four-point-contact on uneven terrain, different from conventional foot systems. However, since WS-1 has some problems, an improved foot system, WS-1R (Waseda Shoes - No.1 Refined) is developed. Through hardware experiments, the effectiveness of WS-1 R is confirmed.