To provide an enclosed rotation sensor device which can be stably maintained in an enclosed state for a long period and is formed by integrally molding a resin.

In an enclosed sensor device 1, a sensor assembly 10 constituted by housing a magnetic core member 5 and a permanent magnet 4 in the hollow section of a bobbin 2 wound with a coil 3 is sealed with a jacket section 7 made of a molded resin. The bobbin 2 is integrally formed so that the front end part 21A of the hollow section 21 can be closed in a bag-like state and the magnet 4 is positioned to the foremost part 21 of the section 21. Then a jacket section 8 for leader lines is formed without using any grommet by coating the leading-out end sections of covered wires 61 and 62 with a polyamide resin and closely adhered to the coatings 61B and 62B of the wires 61 and 62 while elasticity is given to the coatings 61B and 62B and the jacket section 7.