PURPOSE: To obtain coenzyme Q10 useful as a drug, etc. efficiently, by cultivating a bacterium belonging to the genus Erythrobacter, capable of producing coenzyme Q10 in a nutritive medium, separating and collecting prepared coenzyme Q10.

CONSTITUTION: A bacterium [e.g., Erythrobacter OCh101(FERM P-6712), Erythrobacter OCh114(FERM P-6713)] belonging to the genus Erythrobacter, capable of producing coenzyme Q10, is cultivated in a nutritive medium containing a sacchride, organic acid, nitrogen source, inorganic salt, vitamin, etc., at about 5W35°C for about 10hrW7 days aerobically. After the cultivation is over, the mold is collected, extracted with a solvent, recrystallized. etc. repeatedly, to give the desired coenzyme Q10. Since OCh101 strain and OCh114 strain do not yield analogous substances except coenzyme Q10, so that it is separated and purified easily.