The present invention relates to a PPG signal measuring method which is strong against motion noise and is able to solve problems caused by high frequency noise and motion noise generated when measuring a PPG signal which is one of biological signals. The PPG signal measuring method includes: a PPG signal measuring step through multiple channels receiving two or more channels of a PPG signal from an end part of a human body; a high frequency noise removing step of removing the signal noise of a high frequency band using a low-pass filter from the PPG signal measured in the PPG signal measuring step through the multiple channels; a reference signal setting step to determine whether motion noise exists in the PPG signal from which a high frequency is removed through the high frequency noise removing step; a time correcting step for a comparison between multi-channel signals since a time difference exists between a signal measured through multiple channels and a signal detected by a distance difference between each measurement position and a heart; and a motion noise determining and signal selecting step to output a normal signal by comparing the cycle time of the signal of multiple channels corrected in the time correcting step with the cycle time of a reference signal.