The method for adjusting a groove depth includes: preparing masks having different thicknesses on respective top surfaces of a plurality of substrates made of silicon carbide; forming a first opening having a predetermined width and a second opening having a width wider than the first opening in each of the masks; simultaneously forming a first groove and a second groove in each of the substrates by selectively etching via the first opening and the second opening; measuring a depth ratio of the first groove to the second groove in each of the substrates; and acquiring a thickness of a mask such that the depth ratio is an intended value, from a relationship between each thickness of the masks and each depth ratio in the substrate.