A method for estimating a position where an abnormality has occurred in a robot that drives an arm using a servo motor, the method comprising: an abnormality detection step of detecting that an abnormality has occurred; a position detection step of detecting, when occurrence of the abnormality is detected in the abnormality detection step, a position where the abnormality has occurred; a cycle observed value detection step of observing a transition of a value of a current flowing through the servo motor or a position deviation of the servo motor as an observed value, and detecting a representative value of the observed value for each cycle in a prescribed operation of an operation for each cycle in an operation repeatedly performed by the robot; and a daily observed value detection step of detecting a representative value of the observed value for each day from the representative value of the observed value detected for each cycle, wherein when the representative value of the observed value for each day deviates from a prescribed range, the occurrence of the abnormality is detected in the abnormality detection step; and wherein the position detection step includes an estimation step of estimating a position where the abnormality has occurred from a type of value deviating from the prescribed range of the representative value of the observed value for each day detected for a plurality of types, and a waveform obtained by a change of the observed value with the passage of time when the occurrence of the abnormality is detected in the abnormality detection step; wherein in the cycle observed value detection step, a mean square value and a peak value of the observed value in the prescribed operation are calculated for each cycle, and the daily observed value detection step includes: a mean square median calculation step of calculating a median of the mean square value for each day, a mean square standard deviation calculation step of calculating a standard deviation of the mean square value for each day, a peak median calculation step of calculating a median of the peak value for each day, and a peak standard deviation calculation step of calculating a standard deviation of the peak value for each day. an abnormality detection step of detecting that an abnormality has occurred; a position detection step of detecting, when occurrence of the abnormality is detected in the abnormality detection step, a position where the abnormality has occurred; a cycle observed value detection step of observing a transition of a value of a current flowing through the servo motor or a position deviation of the servo motor as an observed value, and detecting a representative value of the observed value for each cycle in a prescribed operation of an operation for each cycle in an operation repeatedly performed by the robot; and a daily observed value detection step of detecting a representative value of the observed value for each day from the representative value of the observed value detected for each cycle, wherein when the representative value of the observed value for each day deviates from a prescribed range, the occurrence of the abnormality is detected in the abnormality detection step; and wherein the position detection step includes an estimation step of estimating a position where the abnormality has occurred from a type of value deviating from the prescribed range of the representative value of the observed value for each day detected for a plurality of types, and a waveform obtained by a change of the observed value with the passage of time when the occurrence of the abnormality is detected in the abnormality detection step; wherein in the cycle observed value detection step, a mean square value and a peak value of the observed value in the prescribed operation are calculated for each cycle, and the daily observed value detection step includes: a mean square median calculation step of calculating a median of the mean square value for each day, a mean square standard deviation calculation step of calculating a standard deviation of the mean square value for each day, a peak median calculation step of calculating a median of the peak value for each day, and a peak standard deviation calculation step of calculating a standard deviation of the peak value for each day. a mean square median calculation step of calculating a median of the mean square value for each day, a mean square standard deviation calculation step of calculating a standard deviation of the mean square value for each day, a peak median calculation step of calculating a median of the peak value for each day, and a peak standard deviation calculation step of calculating a standard deviation of the peak value for each day.