In Japanese public administration, the word “efficiency” has historically been translated as “noritsu”. However, in recent years it is now often generally translated as “koritsu”. This change was effected by the vogue of New Public Management. Although both “noritsu” and “koritsu” are equivalents of the term “efficiency”, people are not aware that “koritsu” is a new concept and is used as a keyword of the administrative reform in Japan. “Efficiency” itself is not integrally defined in each discipline. For example, in the history of public administration, the concept varies by the times was praised and was criticized. Thus, regardless of whether “noritsu” or “koritsu” is used, if people who are concerned with “public” as well as statesmen and civil servants use it as an evaluation standard for policy, programs and projects, it is essential for them to define the concept clearly and discuss its merit and deficiencies in advance.