To provide a rotation detection sensor which is excellent in sealing performance for preventing entry of water from the outside, prevents sensor components and their peripheral circuit portions from being damaged by external force and internal heat distortions due to internal heating and a change in temperature in the external environment, and moreover, which can be manufactured at low cost.

A sensor unit B is constituted of a magnetic-type sensor element 1 for detecting a detecting object of the rotating wheel of a wheel bearing, a cable 10 for extracting the output signal of this sensor element 1 to the outside, and a board 11 to which the sensor element 1 and one end part of the cable 10 are attached, and which has conductive portions 3 electrically connecting the electrode portions 2 of the sensor element 1 to pieces of core wire 4 of the cable 10. This sensor unit B is fixed to a sensor fixing member 7 with the board 11. Water-resistant films 13 are formed on the sensor element 1 in the sensor unit B, the one end part of the cable 10, and the surface and the undersurface of the board 11. A molded part 8 is provided, by performing molding with molding material, and covering the sensor unit B.