An object of the present invention is to provide a crystal of 3′-sialyllactose (hereinafter, referred to as 3SL), which is easily handled, and has high storage stability at normal temperature as well as under high temperature conditions, and provide a process for producing the same. The present invention relates to a 3SL sodium salt n-hydrate (wherein n represents any number of 0 to 9, and when n is 0, it is referred to as 3SL sodium salt anhydrate) and a process for producing the same.