PURPOSE: To enable both culturing of a miroorganism in a high concentration in a short culture time and efficient production of products sparingly soluble in water and culture a microorganism usefully for fermentative production by adding a Ca salt to a culture medium containing an organic solvent.

CONSTITUTION: A microorganism [e.g. Pseudomonas putida var. (FERM BP-1751)], belonging to the genus Pseudomonas and having tolerance to organic solvents is cultured in a culture medium containing an organic solvent (e.g. toluene). In the process, ≥1mM Ca salt (e.g. calcium nitrate) and preferably ≥2mM Mg salt (e.g. magnesium sulfate heptahydrate) are added to the culture medium. Thereby, culturing is carried out.