To obtain an apparatus for designing a prosthetic appliance with which the designing of the prosthetic appliance taking the motion of the jaw into consideration is made possible without increasing the burden on work in daily diagnoses and a method therefor.

This method has a stage S1 for preparing the bimaxillary dentition models including the restoration sections by the prosthetic appliance, a measuring stage S2 for measuring the relative positional relations in the shapes and plural bite positions of these bimaxillary dentition models, a designing stage S5 for computing the bite shape relation of the bimaxillary dentition in any one bite position in accordance with the measurement data and designing the shape of the prosthetic appliance from this relation, a computing stage S7 for computing the bite shape relation of the bimaxillary dentition in another bite position in the state of mounting the prosthetic appliance and a correcting stage S8 for correcting the shape of the prosthetic appliance in accordance with the result of the computation.