This study suggests the basic data required in setting up the standard for the architectural planning of Korean senior center by analyzing the standard and current situation of a senior center in Japan that has the welfare facility system similar to that of Korea and understanding its architectural characteristics. 1) Basic spaces that constitute the senior center in Japan are meeting room, lecture room, library, multipurpose meeting room, conference room, game-recreation room, kitchen, lounge, locker room and office. ADL, kitchen, relaxing room, private bathroom, and special bathroom are needed for adult day care as establishments as an annex and work room is also required for Job training. 2) The area of a senior center is calculated in consideration of its space organization that are required as basic. For the type "A", minimum area of 1,256.42 $m^2$2 and maximum area of 2,050.56$m^2$ and for the type "B", minimum area of 812000$m^2$ and maximum area of 1,604.14$m^2$ are suggested as optimum areas. 3) The circulation planning is presented by the connected between the space organization as well as the circulation system in day care center.