This study was to investigate the amino acid, free amino acid and fatty acid composition of chicken breast muscle and legs muscle by different raising periods (30, 36 and 42 days). In amino acid composition, the glutamic acids were 3.63% at 30 days, 3.63% at 36 days and 3.54% at 42 days in the breast muscle. The glutamic acid contents in the breast and leg muscle were decreasing tendency as raising periods increased. The total free amino acids were 370.6 mg at 30 days, 235.9 mg at 36 days and 246.3 mg at 42 days in the breast muscle, and those were 470.16 at 30 days, 326.4 mg at 36 days and 321.9 mg at 42 days in the leg muscle. Total contents of free amino acids were higher in chicken legs muscle than in chicken breast muscle. The linoleic acids, the most essential fatty acid, were contained 17.84% at 30 days, 17.84% at 36 days and 20.33% at 42 days in chicken breast muscle. These results indicated that the fatty acid composition increased as raising periods increased. There were 0.69% DHA (Docosahexaenoic acid) in chicken breast muscle at 30 days, 0.96% at 36 days and 1.29% at 42 days. From these results, the DHA contents in chickens were also increased as raising periods increased.