Affords a GaN single-crystal mass, a method of its manufacture, and a semiconductor device and method of its manufacture, whereby when the GaN single-crystal mass is being grown, and when the grown GaN single-crystal mass is being processed into a substrate or like form, as well as when an at least single-lamina semiconductor layer is being formed onto a single-crystal GaN mass in substrate form to manufacture semiconductor devices, cracking is controlled to a minimum. The GaN single-crystal mass 10 has a wurtzitic crystalline structure and, at 30 DEG C., its elastic constant C11 is from 348 GPa to 365 GPa and its elastic constant C13 is from 90 GPa to 98 GPa; alternatively its elastic constant C11 is from 352 GPa to 362 GPa.