To provide a safety cerebroprotective agent originated from a food.

The cerebroprotective agent contains a purple sweet potato-fermented liquid as a main component. The purple sweet potato-fermented liquid is obtained, for example, by (1) a step for peeling the skin of the purple sweet potato, treating the surface of the peeled purple sweet potato with citric acid, and freezing the treated purple sweet potato, (2) a step for thawing the frozen purple sweet potato, (3) a step for steaming the thawed purple sweet potato, (4) a step for inserting the steamed purple sweet potato and malted rice into a tank and fermenting the purple sweet potato at 50-70C for 18-28 hr, (5) a step for squeezing the fermented purple sweet potato, and separating the squeezed product into a juice and a solid residue, and (6) a step for regulating the acidity by further adding the citric acid to the juice. The cerebroprotective agent is especially effective for the prevention of cerebral infarction.