The present invention describes an efficient way to isolate a sialic acid from a fermentation broth. The sialic acid contained in the fermentation broth is produced by bacterial fermentation. The inventive process comprises a step of removing biomass from the fermentation broth, a step of subjecting the resulting solution to at least one of a cationic ion exchanger treatment and an anionic ion exchanger treatment and a step of removing salts after the ion exchanger treatment. The process can provide the sialic acid in spray-dried form as well as in form of sialic acid crystals.