To provide an analyzing system for encoder position error which can detect offset voltage components, gaps in amplitude ratio, phase shift, secondary voltage components and tertiary voltage components of encoder signal.

The encoder position error analyzing system comprises a 1st DFT (Diagnostic Function Test)/FFT (Fast-Fourier Transform) analyzer 21 providing frequency analysis of a positional error signal waveform 11; a 2nd DFT/FFT analyzer 22 providing frequency analysis of A phase signal waveform 12; and a parameter analyzer 30 detecting error signal component contained in encoder original waveform, based on the phase information of the primary components resulting from both frequency analyses of the position error signal waveform provided by the 1st DFT/FFT analyzer 21 and the A phase signal waveform by the 2nd DFT/FFT analyzer 22.