A process for producing riboflavin, comprising culturing riboflavin producing fungi in a culture medium in which a vegetable oil or an animal oil is used as a carbon source so as to effect formation and accumulation of riboflavin and harvesting the riboflavin, characterized in that a carrier constituted of a clay mineral capable of adsorbing oil contents or a product of chemical treatment thereof or a calcium compound is incorporated in the culture medium. This process enables carrying out the concentration and recovery of riboflavin at low cost without the need of time-consuming operation, so that riboflavin can be produced in a high production rate with a high yield, and further enables effectively utilizing waste vegetable oils or animal oils to be disposed of for the recovery of riboflavin.