It is believed that quantification and monitoring of daily stress can lead to prevention of various stress-related diseases. In this study, we integrated simultaneously measured electrocardiograms and pulse waves to calculate highly accurate stress values that are not easily affected by noise, and calculated the reliability of each biological signal in a defined analysis interval by performing abnormal peak detection based on the IPFM model. The reliability of the data in the analysis interval is compared as needed, and the stress value of the biological signal with high reliability is adopted to output a time-series graph of stress values with reduced influence of noise.