Recently, bamboo has been reevaluated from the environment-friendly viewpoint. Bamboo is a typical yearly-renewable bio-resource and inherently has an advantage in the high growing speed. With the increase in the use of the bamboo, it is anticipated that the quantity of bamboo powder discharged in the various cutting processes will also increase. It is, therefore, important for bamboo powder to develop an adequate recycling technology. For this purpose, we developed biodegradable composite boards with bamboo powder and a starch-based plastic. It is found that the biodegradable composite boards fabricated with bamboo powder of 0.5mm in diameter had an acceptable high bending strength and high bending modulus. It is also shown that an alkali treatment to the bamboo powder affects the mechanical properties of the biodegradable composite boards with an increased bending strength of about 20 percents.