Japanese social security pension plans started for government officers or militaries in around 1880,and for general workers 1942( Workers Pension Plan), and in 1961 realized “ National universal pension plan”, in which all the people living in Japan were covered by at least one of social security pension plans.

“ National universal pension plan” celebrated 50^thanniversary in 2011.

Japanese government is integrally trying to reform social security and tax system at present.

 This paper will review the history of Japanese social security pension plans development for fifty years and discuss financial issues including,

 1.( Premium ) Japanese social security pension plans adopted “Level premium method”,

2.(Financing) Japanese pension plans started by funding method and gradually changed to partial funding method, and is multi-pillar system composed of social security, corporate and private pension and saving, in addition, in 2004 changed from infinite equilibrium method to finite method,

3.(Benefit level) In Japan benefit level had gradually raised in accordance with high economic growth since mid-1960s, and finally cost-of living adjustment was introduced in 1973, and reduced the level afterwards by slowdown of economic growth

4.(Pensionable age) Though pensionable age had gradually increased with life span increased, it was usually very difficult and took much time to do it, and

5.(Pension syatem) Fiscal adjustment has been done among employee pension plans in 2012.

 Social security pension plans developments in a country are thought to be highly path dependent by their social, ecomic, or financial situations. However economic and informational globalization has developed recently. Authors hope that lessons from Japanese Social Security Pension Plans for 50 years would be beneficial to other countries, particularly those discussing the introduction of social security pension plans.