It is possible to quantify a fatigue degree and display it. A fatigue degree measuring device (1) includes: biological signal peak value detection means (23) for detecting a peak value of each cycle of the raw waveform of biological signal data; power value calculation means (24) for calculating a difference between the peak value of the upper limit side and a peak value of the lower limit side for predetermined time range from the peak values obtained from the biological signal peak value detection means (23) and setting the difference as a power value; and power value inclination calculation means (25) for calculating the inclination of the power value. The time-series signal of the power value inclination is subjected to an absolute value processing and an integrated value is calculated. The integrated value is obtained as a fatigue degree. Thus, it is possible to quantify the human fatigue degree.