Abstract: A high-voltage transformer winding bobbin made from a heat-resisting, insulative plastic material through the process of injection molding, which includes a plurality of square flanges equidistantly spaced around the hollow, cylindrical, square body thereof and a plurality of winding grooves respectively defined between each two adjacent square flanges for winding an enamel wire, wherein the square flanges except the last one, have each a V-shaped wire guiding notch on a respective peripheral edge. The V-shaped wire guiding notches on the square flanges are respectively aligned for guiding an enamel wire into each winding groove. In an alternate form, the V-shaped wire guiding notches on the square flanges of odd numbers are aligned and respectively disposed diagonal to the V-shaped wire guiding notches on the square flanges of even numbers.