The effect of coarser grains in AlN raw material on the inhomogeneous structure in AlN sintered body was investigated. It was confirmed that the fine and homogeneous AlN raw material showed higher densification rate at lower temperature, namely, a high sinterability. On the other hand, the addition of coarser grains to the fine and homogenous raw material restricted densification to bring about lower density. As a result of measurement of local porosity and pore size distribution, it was observed that large pores were unevenly distributed near coarser grains. The reason why large pores were left near coarser grains seems to be that not only the coarser grain disturbed shrinkage but also that oxygen, essential for densification of AlN, was insufficient near the coarser grains.