The magnetic sensing portion 30 of the rotation sensing device comprises three magnetic sensors 31-33 and a substrate 45 for mounting these magnetic sensors, with each magnetic sensor comprising a magnetic wire 34 generating large Barkhausen effects, a coil 35, and a bobbin 36. The magnetic sensors are disposed on the substrate 45 such that the directions of extension of the magnetic wires 34 are parallel to the substrate 45, the magnetic sensing portion 30 is disposed on the outer periphery of the trackway of the magnetic field forming portions such that the directions of extension of the magnetic wires 34 are parallel to the axial direction of the rotary shaft 3, and the location of the magnetic wire installation portion 38 in the bobbin 36 of each magnetic sensor is configured such that the respective magnetic wires 34 of the three magnetic sensors are respectively equidistant from the rotary shaft 3.