Alcaligenes eutrophus transformants harboring rite cloned phbCAB, phbAB, and phbC genes were cultivated under various culture conditions to determine the optimal cultivation condition for an effective accumulation of poly-beta-hydroxybutyrate. The transformants showed significantly increased total cell growth and PHB accumulation due to the increased activities of enzymes of PHB biosynthesis. In the batch cultivation, the transformant can synthesize PHB more favorably at the high C/N, molar ratio and low carbon concentration compared to the parent strain, The fedbatch cultivation was confirmed to be a more effective method for maximizing the effect of cloned genes to PHB biosynthesis compared to the batch cultivation. The plasmid stability was maintained at around 85% after 36 h and elongated morphological changes of transformant at the early growth stage was observed The gene amplification through the transformation of cloned PHB biosynthesis genes in A. eutrophus seems to be an excellent method for strain improvement to achieve an effective accumulation of PHB.