A rotary encoder comprising: a stator; a first rotor affixed to a rotation shaft and rotatable with the rotation shaft, the first rotor opposing the stator in an axial direction; a second rotor positioned about the external circumference of the first rotor and rotatable relative to the first rotor, the second rotor opposing the stator in the axial direction; a rotation transmitter configured to rotate the rotation shaft, and further configured to rotate the second rotor at a different speed than the first rotor; first and second angle detection tracks coaxially positioned about the rotation shaft on a surface of the stator opposing the first rotor and on a surface of the first rotor opposing the stator, wherein the first angle detection track is radially inside of the second angle detection track; and third and fourth angle detection tracks coaxially positioned about the rotation shaft on a surface of the stator opposing the second rotor and on a surface of the second rotor opposing the stator, wherein the third angle detection is radially inside of the fourth angle detection track, wherein: the first angle detection track generates an N, time cyclic change at one rotation of the first rotor; the second angle detection track generates an N 2 time cyclic change at one rotation of the first rotor; the third angle detection track generates an N 3 time cyclic change at one rotation of the second rotor; the fourth angle detection track generates an N 4 time cyclic change at one rotation of the second rotor; and N 1 is different from N 2, and N 3 is different from N 4. a stator; a first rotor affixed to a rotation shaft and rotatable with the rotation shaft, the first rotor opposing the stator in an axial direction; a second rotor positioned about the external circumference of the first rotor and rotatable relative to the first rotor, the second rotor opposing the stator in the axial direction; a rotation transmitter configured to rotate the rotation shaft, and further configured to rotate the second rotor at a different speed than the first rotor; first and second angle detection tracks coaxially positioned about the rotation shaft on a surface of the stator opposing the first rotor and on a surface of the first rotor opposing the stator, wherein the first angle detection track is radially inside of the second angle detection track; and third and fourth angle detection tracks coaxially positioned about the rotation shaft on a surface of the stator opposing the second rotor and on a surface of the second rotor opposing the stator, wherein the third angle detection is radially inside of the fourth angle detection track, wherein: the first angle detection track generates an N, time cyclic change at one rotation of the first rotor; the second angle detection track generates an N 2 time cyclic change at one rotation of the first rotor; the third angle detection track generates an N 3 time cyclic change at one rotation of the second rotor; the fourth angle detection track generates an N 4 time cyclic change at one rotation of the second rotor; and N 1 is different from N 2, and N 3 is different from N 4. the first angle detection track generates an N, time cyclic change at one rotation of the first rotor; the second angle detection track generates an N 2 time cyclic change at one rotation of the first rotor; the third angle detection track generates an N 3 time cyclic change at one rotation of the second rotor; the fourth angle detection track generates an N 4 time cyclic change at one rotation of the second rotor; and N 1 is different from N 2, and N 3 is different from N 4.