A custom-made stem has a shape displaying good fit and fill, reflecting personal characteristics of a femur obtained by computer calculation. A model is made from the femur which does not need much time to calculate in spite of the fact that it complies with the characteristic of shape of the femur, particularly with the personal difference in the curvature thereof, which usually complicates the calculation. Several models are made which can be implanted in a deep hollow by calculating in a reverse course how the stem is pulled out of the deep hollow, to display reliable models to a surgeon. By determining the movement peculiar to the stem of a particular patient, an improved stem is made in a short time which meets the needs of the surgeon. The stem, which is custom-made, can be confirmed beforehand that it agrees with the femur of the patient.