To provide a method for casting a pump casing having guide vanes by which the generation of internal defects in cast products is avoided, variance of cast quality is controlled and reliability on product precision is improved by dissolving faults causing a large number of cast burrs to cast products and improving gas purging.

A guide vane core mold 3 is molded by vertical molding by positioning the inflow side of the core mold in the upper part and moreover by jointly using a scraping mold for filling a casting material 9 for the inflow side part. Casting is executed by arranging the cast guide vane core mold 3 between the outer surface mold 1 which forms the outer surface of a casing outer cylinder and the inner surface mold 5 which forms the inner surface of a casing inner cylinder in the state that the inflow side of the guide vanes is positioned in the upper part.