Provided is a rotation angle detecting device with high detection accuracy, which can be structured with a small number of teeth even if a shaft angle multiplier increases, thus enhancing winding workability and becoming suitable for mass production. The rotation angle detecting device includes: a stator formed of an iron core with teeth, the stator including: an exciting winding of one phase or more; and output windings of two phases or more; and a rotor with a salient pole, in which numbers of turns of the output windings of the two phases each have a value obtained by a function containing a sum or a difference between a sine wave of an order equal to an absolute value of a sum of a number of the salient poles and a number of the pole pairs, and a sine wave of an order equal to an integer that is different from an absolute value of the number of the pole pairs of the exciting winding and different from an absolute value of a difference obtained by subtracting the number of the salient poles from the number of the pole pairs.