A plastic working method for workpiece material, comprising: - a workpiece material retaining step for retaining a workpiece material in part of a groove of a first mold, the groove being for retaining the workpiece material and being formed at least partly into a generally linear shape; - a first fitting step for fitting a first guide portion of a second mold to a place of the groove where the workpiece material is not placed, the second mold having the first guide portion to be relatively movably fitted to the groove, and further having a body portion having a through hole intersecting and communicating with the groove with the first guide portion fitted to the groove; and - a workpiece material push-in step for making the first mold moved relative to the second mold with the first guide portion fitted to the groove so that the workpiece material substantially immovably retained in the groove of the first mold is bent by the first guide portion and pushed from the groove into the through hole; characterised in that: - the second mold has a second guide portion, - the method further comprising: a second fitting step for fitting the second guide portion of the second mold to a groove of a third mold, the third mold having the groove to which the second guide portion is to be fitted and which is to communicate with the through hole with the second guide portion fitted to the groove and moreover which is formed at least partly into a generally linear shape; and - a retaining step for retaining a state that the first guide portion is fitted to the groove of the first mold while the second guide portion is fitted to the groove of the third mold, wherein - in the workpiece material push-in step, at least part of the workpiece material is pushed into the groove of the third mold via the through hole. - a workpiece material retaining step for retaining a workpiece material in part of a groove of a first mold, the groove being for retaining the workpiece material and being formed at least partly into a generally linear shape; - a first fitting step for fitting a first guide portion of a second mold to a place of the groove where the workpiece material is not placed, the second mold having the first guide portion to be relatively movably fitted to the groove, and further having a body portion having a through hole intersecting and communicating with the groove with the first guide portion fitted to the groove; and - a workpiece material push-in step for making the first mold moved relative to the second mold with the first guide portion fitted to the groove so that the workpiece material substantially immovably retained in the groove of the first mold is bent by the first guide portion and pushed from the groove into the through hole; - the second mold has a second guide portion, - the method further comprising: a second fitting step for fitting the second guide portion of the second mold to a groove of a third mold, the third mold having the groove to which the second guide portion is to be fitted and which is to communicate with the through hole with the second guide portion fitted to the groove and moreover which is formed at least partly into a generally linear shape; and a second fitting step for fitting the second guide portion of the second mold to a groove of a third mold, the third mold having the groove to which the second guide portion is to be fitted and which is to communicate with the through hole with the second guide portion fitted to the groove and moreover which is formed at least partly into a generally linear shape; and - a retaining step for retaining a state that the first guide portion is fitted to the groove of the first mold while the second guide portion is fitted to the groove of the third mold, wherein - in the workpiece material push-in step, at least part of the workpiece material is pushed into the groove of the third mold via the through hole.