The purpose of this study were to investigate the difference of job competencies according to the age in clerical workers. To achieve of the purpose, NCS(National Competency Standards) for clerical workers and WAI(Work Ability Index) were employed for survey questionnaire. The survey were conducted 1,216 workers who sampled by age groups and subcategories of clerical work. The results of this study were as follows. All of three job competencies were showed inverted U-shape by age, and inflection age was different among three job competencies. which key competency was 40, basic competency was 42, and work ability was 35. This result was different from preceding studies, which was owing to job differences. In addition, the different shapes of change in competency level were found, which could be attributed to differences in components of job competencies.