The invention discloses a manufacturing method of a spring assembly. The spring assembly includes: a substrate; a coil spring having an end turn portion fixed to the substrate; a tubular inner wall extending from the substrate along the inner peripheral side of the coil spring and playing the spring fixation wall action of preventing the end turn portion of the coil spring from coming off in an axial direction, and an outer wall extending from the substrate along the outer peripheral side of the coil spring and playing the support wall action of preventing the end turn portion of the coil spring in a radial direction, wherein the end turn portion of the coil spring is partially and coaxially arranged on the tubular inner wall, and a gap is formed between the end turn portion and the outer wall, the diameter of the tubular inner wall is enlarged by implementing a staking step so as to stake the end turn portion of the coil spring, and the end turn portion of the coil spring is enlarged along the radial direction so as to be contacted with the outer wall.