The purpose of this study was to clarify the realities of the career maturity on the early career nurses, and to clarify the factors affecting their career maturity as professional nurse. From June to July in 2012, 195 early career nurses who were extracted from seventeen Red Cross hospitals in Japan were investigated, and on them relationship between their professional career maturity and self-education, self-efficacy, social support in workplace, and experience were analyzed. 195 early career nurses were that first year nurses were 61, second year nurses were 73, and third year nurses were 61. Their career maturity average scores showed the tendency to decrease with years of experience, following that first year nurses score was 92.5 points, second year nurses score was 89.5 point, and third year nurses score was 87.0 points and their differences were not statistically significant. Career maturity scores of nurses who received a basic education in university were significantly higher than nurses who received a three-year basic education. Between all factors of the career maturity and all factors of self-education scores, the moderate or low correlation was observed. Correlation was also observed between the scores of autonomous factors of career maturity and the scores of all factors of social support in workplace. Especially the scores of support by senior nurses showed medium correlation with the score of autonomous factor of career maturity. These results suggest that support for early career nurses by senior nurses is important to promote their professional maturity.