To provide a rotation detection device and its manufacturing method adapting to an increase in the types of rotation detection ICs at low cost.

The rotation detection device comprises: a rotation detection section which detects the rotation of a rotating body and outputs its rotation detection signal; a case-shaped housing having hollow shape of which one end is an inlet and the other end is blocked and into which the rotation detection section is inserted to be fixed; and a shape adjustment section formed by resin molding so that the rotation detection section is covered to match the shape of the rotation detection section to the internal shape of the housing. A method of manufacturing the rotation detection device is also provided.