Torque sensor and electric power-steering device

In this torque sensor for an electric power-steering device, a physical quantity produced by a torque-sensor mechanism is increased near the center (neutral position) of a steering wheel, providing the driver with a natural, crisp steering feel. A torsion bar (3) for use in said torque sensor has a torsion-bar core (3A) and a torsion-bar tube (3B). The torsion-bar tube (3A) comprises a set of tubular components (3Ba, 3Bb) and accommodates the torsion-bar core (3A) thereinside. Both ends of the torsion-bar core (3A) are anchored inside the torsion-bar tube (3B). When twisting exhibited by the torsion-bar core (3A) reaches a prescribed angle of rotation, the set of cylindrical components (3Ba, 3Bb) mesh together via meshing teeth (3Bat, 3Bbt) so as to become coupled together, forming a single torsion bar. The elastic force produced by the torsion-bar tube (3B) is greater than the elastic force produced by the torsion-bar core (3A).