In a cold coil forming process, a pitch control tool is moved in synchronism with the displacement of the outer diameter control roller so as to form a coil spring having a straight and oblique axial line, and, at the same time, maintain a pitch of the coil wire substantially constant substantially over an entire length thereof. Thus, the method of the present invention can be implemented by using a conventional coiling machine only if the outer diameter control roller and the pitch control tool can be adjusted as required by the present invention. In particular, the pitch of the coil spring can be kept constant over each turn of the coil wire without regard to the variation in the radius of curvature of the coil spring.