Abstract: The present invention provides a novel biomass plastic. The biomass plastic of the present invention is an alternative to polyethylene terephthalate and is composed of an adhesive polymeric substance. The biomass plastic is obtained by a production method including the steps of: (1) culturing a microorganism mixture composed of Bacillus subtilis, Bacillus pumilus, and Bacillus thuringiensis at 30 to 50° C. for 12 hours to 4 days in an environment (medium) including starch and silicic acid or a silicate acceptable in microbial culture; (2) subsequently adding Corynebacterium glutamicum thereto and culturing it at 30 to 50° C. for 12 hours to 4 days; and (3) collecting the adhesive polymeric substance from culture obtained.