The present invention relates to a stress analysis method including: acquiring bio-signals from a test subject; calculating a probability of each of a plurality of stress level values by processing the bio-signals using a deep neural network algorithm; estimating a stress level value with the maximum probability of the plurality of stress level values as a stress level value of the test subject; determining usefulness of the estimated stress level value; and outputting the estimated stress level value determined to be useful through the determination of usefulness, as the final stress level.