An angle detector for detecting an angle change amount of a rotary body rotating around a rotary axis, the angle detector comprising a scale with multiple graduations along a circumference of the rotary body in a rotating direction, at least two sensors (201a - 201i) disposed along the circumference, each of the at least two sensors (201a - 201i) outputting a signal in accordance with the angle change amount based on the multiple graduations, and a controller receiving the output signals from the at least two sensors (201a -201i) to obtain the angle change amount from the output signals; wherein the output signal contains a fundamental wave component of which one cycle corresponds to an angle interval between two adjacent graduations of the multiple graduations and which is set as a first order, and a harmonic component which has an order higher than the first order; characterized in that the number of the at least two sensors (201a - 201i) is determined in order to remove from the angular change amount at least one angle error component owing to the harmonic component, the at least one angle error component having an order component of an integer multiple of a first order component of which one cycle corresponds to the angle interval; and the number of the at least two sensors (201a - 201i) is determined based on a remainder as follows:. a. the electrical angle error being expressed by order N p = N x p wherein N being the number of graduations of scale and p being order of angle error component of the single graduation, b. the order N p of the electrical angle error on the circumference of the scale is divided by the integer as the number of the planned sensor locations and the remainder being a fraction is obtained, and c. if the remainder becomes larger, the number of the order N p of the electrical angle error that can be removed becomes larger, d. depending on the remainder, calculating a score of the number of the planned sensor locations, e. results of the number of the planned sensor locations with higher total score are determined, f. the one with higher total score being capable of removing more electrical angle errors with the orders. the output signal contains a fundamental wave component of which one cycle corresponds to an angle interval between two adjacent graduations of the multiple graduations and which is set as a first order, and a harmonic component which has an order higher than the first order; characterized in that the number of the at least two sensors (201a - 201i) is determined in order to remove from the angular change amount at least one angle error component owing to the harmonic component, the at least one angle error component having an order component of an integer multiple of a first order component of which one cycle corresponds to the angle interval; and the number of the at least two sensors (201a - 201i) is determined based on a remainder as follows:. a. the electrical angle error being expressed by order N p = N x p wherein N being the number of graduations of scale and p being order of angle error component of the single graduation, b. the order N p of the electrical angle error on the circumference of the scale is divided by the integer as the number of the planned sensor locations and the remainder being a fraction is obtained, and c. if the remainder becomes larger, the number of the order N p of the electrical angle error that can be removed becomes larger, d. depending on the remainder, calculating a score of the number of the planned sensor locations, e. results of the number of the planned sensor locations with higher total score are determined, f. the one with higher total score being capable of removing more electrical angle errors with the orders. a. the electrical angle error being expressed by order N p = N x p wherein N being the number of graduations of scale and p being order of angle error component of the single graduation, b. the order N p of the electrical angle error on the circumference of the scale is divided by the integer as the number of the planned sensor locations and the remainder being a fraction is obtained, and c. if the remainder becomes larger, the number of the order N p of the electrical angle error that can be removed becomes larger, d. depending on the remainder, calculating a score of the number of the planned sensor locations, e. results of the number of the planned sensor locations with higher total score are determined, f. the one with higher total score being capable of removing more electrical angle errors with the orders.