PURPOSE: To manufacture a groove with high accuracy by exact pitch and depth, by forming an almost cylindrical body by bending a base material along a slit formed together with the groove on a plate base material, when manufacturing the nearly cylindrical body having plural grooves on the inside circumferential face.

CONSTITUTION: For instance, in case of manufacturing a cylindrical body having a lot of grooves on the inside circumferential face of a stator of a linear motor, etc., a lot of grooves 2 are provided in parallel and at prescribed intervals and depth on one face of a plate base material 3. Also, plural slits 4 of prescribed depth, being orthogonal to the groove 2 are provided at constant intervals on the base material 3 so that the base material is bent easily. Subsequently, the base material 3 is bent successively along the slit 4 so that the groove 2 becomes the inside, and a nearly cylinderical body is obtained. Thereafter, both end parts 3a, 3b of this base material 3 are joined, and an object nearly cylindrical body is obtained.