It was previously noted that a flavinmononucleotide-like substance was found in the culture solution of Rhizopus oryzae containing riboflavin. In this paper, this flavin was revealed chemically and enzymatically to be a new flavinmonophosphate in which phosphate was attached to a flavinmononuclestide in which phosphate is attached to 3', 2', 5'or 2', 3'of ribityl radical.