A groove shape and an inspection method capable of securely recognizing existence of a weld flaw of a single butt weld zone by a nondestructive inspection, such as a radiograph test or an ultrasonic test, are provided. A groove shape where a concave portion 5 is formed on a butt surface 1b and a butt surface 2b of pipes 1, 2 which are weldments to be welded is prepared and the weld zone welded by single butt welding is inspected by a nondestructive inspection such as a radiograph test or an ultrasonic test.