An object of the present invention is to provide a high-expansion gypsum composition in which the expansion coefficient of a general purpose dental gypsum material or the like is simply and effectively improved to such an extent that has never been achieved with conventional technologies without using any special material by adding an inexpensive additive even in a small addition amount, and furthermore another object of the present invention is to provide a high-expansion gypsum composition the setting expansion coefficient of which is appropriately controlled so that the contraction of a resin to be used can be precisely dealt with, the high-expansion gypsum composition being useful for manufacturing a reproduction model to be used in manufacturing a “non-clasp denture” having no problem in, for example, occlusion (adaptability). The objects of the present invention are achieved by means of a method for producing a high-expansion gypsum composition, the method producing a gypsum composition having an enhanced setting expansion coefficient by copulverizing in a dry system a powdered gypsum composition containing calcined gypsum as a main component and dihydrate gypsum.
