To provide a method suited for manufacturing a magnetic change detecting sensor, wherein the coaxial degree of a cover to a coil assembly is improved and hence the wall thickness of a lower cover is uniform in the circumferential direction.

In this manufacturing method of a magnetic change detecting sensor composed of a bobbin 24, having a cable connector 27 for connecting a detected signal transmitting cable 37 to a coil 26 at the upside of a mounting bracket 35 and a coil winder 28 wound with a coil 26 at the downside of the bracket 35, a pole body 25 coaxially inserted in the bobbin 24 for detecting the magnetic change, and a cover 41 which covers and protects a coil assembly 23 composed of the bobbin 24 and the pole body 25 and integrates the cable 37 and the mounting bracket 35 with the coil assembly 23, a lower top end 25a of the pole body 25 and the top of the coil assembly 23 are held to form the bottom of the cover 41 by the primary molding, and the bottom cover 29 formed by the primary molding is held to form the top of a cover 41 in the secondary molding.