A method for preparing a PRP conjugate having high storage stability and a method for producing a Hib conjugate vaccine are provided. A method for preparing PRP conjugate in accordance with the embodiments of the present invention is characterized by that the release of PRPs after preparing the PRP conjugate is suppressed by using PRP with a lowered molecular weight than native PRP for a coupling reaction between PRP and a carrier protein. Also, a Hib conjugate vaccine comprising as an antigen the PRP conjugate prepared by said method has excellent storage stability and maintain sufficient immunogenicity.
