The present invention affords a method of growing large-scale, high quality Al x Ga 1- x N single crystal. An Al x Ga 1- x N single crystal growth method of the present invention is provided with: a step of preparing an Al y Ga 1- y N (0 < y ‰¤ 1) seed crystal (4) whose crystal diameter D mm and thickness Tmm satisfy the relation T < 0.003D + 0.15; and a step of growing Al x Ga 1- x N (0 < x ‰¤ 1) single crystal (5) onto a major surface (4 m ) of the Al y Ga 1- y N seed crystal (4) by sublimation growth.
