A method of manufacturing a pipe coupling that prevents leakage including: forming a semi-tubular portion and flat portions along opposite sides of the semi-tubular portion; deforming the flat portions to produce larger bending depth and smaller width; bending portions of the flat portions so that the bent portions form acute angles in relation to the semi-tubular portion with sloping flat portions extending from the semi-tubular portion, and distal narrow flat portions; pushing the sloping flat portions away from the semi-tubular portion; pressing the semi-tubular portion, the sloping flat portions, and the narrow flat portions to produce a final shape; and removing burrs so that the semi-tubular portion of the final shape comes into close contact with an outer circumferential surface of a pipe, and the final flat portions are integrally formed along opposite side edges of the semi-tubular portion in a common plane.