1. An analysis method for analyzing an anterior ocular segment tomographic image of an eye to be inspected, the analysis method comprising: determining an approximated line that approximates a shape of an anterior surface of an iris of an anterior ocular segment of the eye to be inspected along the anterior surface of the iris in the anterior ocular segment tomographic image; determining an approximated line extended part obtained by extending the approximated line until the approximated line crosses a baseline in contact with an inner surface of a cornea and an inner surface of a sclera of the anterior ocular segment in the anterior ocular segment tomographic image; and calculating an opening degree of an anterior chamber angle of the anterior ocular segment through use of the approximated line and the approximated line extended part.