To obtain the subject new microorganism, capable of remarkably increasing the production amount of a heterogene product by culturing and useful for production, etc., of an epidermal cell growth factor, etc., by holding the heterogene in a chromosome and further holding an expression vector bonding the heterogene thereto.

This transformant microorganism is a new transformant microorganism, obtained by holding a heterogene (e.g. a gene for expressing an epidermal cell growth factor) in a chromosome and further holding an expression vector having the heterogene bonded thereto such as a microorganism of the genus Bacillus (e.g. Bacillus brevis HPD31-int2) and capable of remarkably increasing the production amount of a heterogene product such as the epidermal growth factor by culturing the microorganism in a culture medium. The transformant microorganism is prepared by integrating a neomycin-resistant gene, a promoter of a cell wall protein gene and the heterogene such as a human epidermal cell growth factor into a plasmid obtained from a microorganism, etc., of the genus Bacillus preparing a recombinant plasmid and transducing the resultant plasmid into the microorganism of the genus Bacillus, etc., according to an elecrtoporation method, etc.