To provide a method for manufacturing a master mold for mass-producing casting with which quantity and cost of the casting, and facility investment and work environment, are improved in comparison with the conventional method.

This method for manufacturing the master mold, is performed, by which the surface layer of the mold is used with thermosetting resin coated sand and the back sand thereof is backed up with furan or organic self- hardening sand, and the hardening of the furan self-hardening sand is quickened by utilizing the reduced pressure to improve the productivity.