A production method for a trimmer line for use with a string trimmer, the production method comprising: a notch forming step of forming a notch row constituted by a large number of notch portions oriented in a same direction, on an outer periphery of a line body along a longitudinal direction of the line body; characterized in that further comprising: a twisting step of twisting the line body that has undergone the notch forming step, whereby obtaining the trimmer line in which the notch portions constituting the same notch row are oriented in different directions, wherein the line body has an outer peripheral surface of a rhombus-shaped cross section, the outer peripheral surface comprising: a first face; a second face forming an acute angle with respect to the first face; a third face forming an obtuse angle with respect to the second face; and a fourth face forming an acute angle with respect to the third face and forming an obtuse angle with respect to the first face, and in the notch forming step, the one notch row is formed along a ridgeline between the first face and the second face, and the other notch row is formed along a ridgeline between the third face and the fourth face, the notch portion is not provided in a part along a ridgeline of a corner portion formed by the second face and third face and in a part along a ridgeline of a corner portion formed by the fourth face and the first face. a notch forming step of forming a notch row constituted by a large number of notch portions oriented in a same direction, on an outer periphery of a line body along a longitudinal direction of the line body; characterized in that further comprising: a twisting step of twisting the line body that has undergone the notch forming step, whereby obtaining the trimmer line in which the notch portions constituting the same notch row are oriented in different directions, wherein the line body has an outer peripheral surface of a rhombus-shaped cross section, the outer peripheral surface comprising: a first face; a second face forming an acute angle with respect to the first face; a third face forming an obtuse angle with respect to the second face; and a fourth face forming an acute angle with respect to the third face and forming an obtuse angle with respect to the first face, and in the notch forming step, the one notch row is formed along a ridgeline between the first face and the second face, and the other notch row is formed along a ridgeline between the third face and the fourth face, the notch portion is not provided in a part along a ridgeline of a corner portion formed by the second face and third face and in a part along a ridgeline of a corner portion formed by the fourth face and the first face. a first face; a second face forming an acute angle with respect to the first face; a third face forming an obtuse angle with respect to the second face; and a fourth face forming an acute angle with respect to the third face and forming an obtuse angle with respect to the first face, and in the notch forming step, the one notch row is formed along a ridgeline between the first face and the second face, and the other notch row is formed along a ridgeline between the third face and the fourth face, the notch portion is not provided in a part along a ridgeline of a corner portion formed by the second face and third face and in a part along a ridgeline of a corner portion formed by the fourth face and the first face.