With recent advances in computers, the finite element method has been used for stress analysis of bone. In particular, the dynamic behavior of the jaw bone has been a subject of interest and analyzed by this method. However as the elastic modulus needed for this method, a uniform value is used without considering differences according to site or direction. Therefore, we measured the elastic modulus at various sites and in various directions of the mandible in adults and children. In addition, the association between the elastic modulus and histological structures was evaluated. Ten specimens of dried mandible from human adults and children were used. The elastic modulus was measured in two regions prepared by equally dividing the ramus of the mandible into lower and upper regions. Samples of 6 mm x 960 microns x 425 microns were collected from the buccal compact bone. The elastic modulus was measured using a three-point bending test. After measurement, the direction of the osteon was examined using SEM. The porosity ratio was also measured after CMR were taken. In both adults and children, anisotropy in the elastic modulus of each direction in the upper region was similar to the anisotropy in unidirectional fiber reinforced composite materials, but not in the lower region. The elastic modulus decreased slightly with an increase in the angle of the direction of osteons to the longitudinal axis of specimens. The direction of osteon may significantly influence anisotropy in the elastic modulus. The elastic modulus in adults was higher than in children in all directions. The porosity ratio in adults was smaller than that in children in all directions. The difference in the porosity ratio between adults and children may significantly influence the value of the elastic modulus.