A method of manufacturing a developing roller, including: a first rolling process for forming a first inclined groove which is continuous in a helical shape, by rotating a first die having blades inclined with respect to an axial direction and a circumferential direction, and a non-bladed die, and feeding an unprocessed developing roller between the first die and the non-bladed die; and a second rolling process for forming a second inclined groove which is continuous in a helical shape and intersects with the first inclined groove, by rotating a second die having blades inclined with respect to an axial direction and a circumferential direction in the direction opposite to that of the first die, and the non-bladed die in the same direction opposite to that in the first rolling process, and feeding the developing roller between the second die and the non-bladed die.