To provide an angle detector for accurately detecting angle for a long time by a self-calibration in the condition that the angle detector is fitted in a machinery device such as a rotating machine.

This self-calibrating type angle detector is constituted by being provided with an interpolation circuit 3 for converting an absolute data 1b detected by an angle signal detecting unit 1 to a fine data 3a, a first calibration unit 4 for computing a first calibration value for calibrating the fine data 3a when rotating an encoder disk at unfixed speed in response to the rotating angle of the encoder disk, and a second calibration unit 5 for computing a second calibration value for calibrating the fine data 3a when rotating the encoder disk at a fixed speed on the basis of a second reference signal not containing an error to be output in response to the rotating speed of the encoder disk.