The present invention relates to a process for producing reduced coenzyme Q10 which comprises obtaining microbial cells containing reduced coenzyme Q10 at a ratio of not less than 70 mole % among the entire coenzymes Q10, optionally disrupting the cells and recovering thus produced reduced coenzyme Q10. The present invention also relates to a process for producing oxidized coenzyme Q10 which comprises either recovering oxidized coenzyme Q10 after oxidizing the above-mentioned microbial cells or disrupted product thereof, or recovering reduced coenzyme Q10 from the above-mentioned microbial cells or disrupted product thereof to oxidize thus-obtained reduced coenzyme Q10 thereafter. According to the processes of the present invention, reduced coenzyme Q10 and oxidized coenzyme Q10 can be produced simply on the industrial scale.