The invention discloses a rotating speed sensor, comprising a housing (1); a segment of external threads (11) are arranged on the outside of a left end of the housing (1); a left stepped hole (2), a middle stepped hole (3) and a right stepped hole (4) are axially arranged in the housing (1); an epoxy resin sleeve (21) is embedded in the left stepped hole (2); the epoxy resin sleeve (21) is internally provided with a Hall element (22) and a neodymium boron iron magnetic steel (23); the middle stepped hole (3) is internally provided with a printed circuit board combination (31), a sleeve (32) and a mounting sleeve (33); the right stepped hole (4) is also internally provided with an aviation plug (41). The rotating speed sensor is provided with the external threads, and the housing is internally provided with the epoxy resin sleeve, allowing a relevant circuit board to be arranged in a relatively sealed space; the housing is prepared by stainless steel materials, and possesses the functions of dust prevention and corrosion protection; the rotating speed sensor has a reasonable and compact structure, is convenient to assemble and disassemble, and can prolong the service life of a product.