A jaw-relation reproduction condition is determined by measuring a jaw movement of a patient, and reproducing a jaw state of the patient on an occlusion-state reproducing apparatus in accordance with the jaw-relation reproduction condition. Dentures are arranged on the apparatus in accordance with the jaw-relation reproduction condition to prepare pre-grinding dentures. Denture data with reference points which is three-dimensional image data containing reference points that represents a positional relationship between the jaw-relation reproduction condition and the dentures and an occlusal surface of the dentures. An occlusion state of the denture data with the reference points is reproduced by using the jaw-relation reproduction condition on a three-dimensional image. Grinding data of a grinding portion is determined under a dynamic condition or set condition from a portion surrounded by an image of upper and lower jaws on the three dimensional image in a reproduced occlusal state.