Rotation-angle detecting device capable of precisely detecting absolute angle

A rotation-angle detecting device for detecting the absolute angle based on a first detection signal that includes sawtooth continuous pulses, each having a portion that gradually and linearly rises and a portion that sharply falls within a detection range, and a second detection signal that rises or falls stepwise within the detection range,

• wherein the second detection signal includes, corresponding to the pulses of the first detection signal, a plurality of flat portions and a plurality of gradually rising or falling portions for linking the flat portions, and each of the gradually rising or falling portions corresponds to the sharply falling portion of the first detection signal, and
• wherein, when the value of the second detection signal is included in any of the flat portions, the absolute angle is found on the basis of the values of the first detection signal and the second detection signal, and, when the value of the second detection signal is included in any of the gradually rising or falling portions, the absolute angle is found on the basis of the value of the first detection signal in conjunction with the value of the second detection signal corresponding to a flat portion preceding or following the gradually rising or falling region.