An electrical speed sensor having a pair of relatively confrontingly rotatable pole members one of which is fixed to the transmission housing of a vehicle while the other members being connected for rotation to a shaft driven by an output shaft of the transmission, characterized by provision of a shaft coupling interposed between the shaft and the said one of the pole mmebers and being rigid in torsion only, to thereby block transmitting of any deflection from the shaft to the said one of the members, with an accurate electric output from the sensor ensured.