There is provided a method of calculating an index for deciding the necessity of surgically operating on the jaw in orthodontic treatment wherein an index for deciding the necessity of surgically operating on the jaw which becomes objective materials for a dentist to decide the necessity of surgically operating on the jaw of a patient in orthodontic treatment of the patient can be calculated easily, and by appropriately combining the results of other inspection methods, the dentist is able to diagnose easily with high objectivity and correctness, moreover with a short period of time, and its program.Using the distance (S-A) between S and A, the distance (S-Xi) between S and Xi (i is an integer from 1 to 4. X1=B, X2=Pog, X3=Gn and X4=Me.) and the distance (Go-Xj) between Go and Xj (j is an integer from 1 to 4. j=i or j≠i.) which are measured by the cephalometric radiography of a patient, an index for deciding the necessity of surgically operating on the jaw in orthodontic treatment is calculated by calculating P= ((S-Xi) + (Go-Xj)) / (S-A) .
