A method and device for measuring a biological variable are provided. The method of measuring the biological variable may include detecting an infrared signal which is irradiated toward a body part and is reflected therefrom, extracting spectrum data from the detected infrared signal, obtaining intensity data corresponding to a preset frequency from the extracted spectrum data, obtaining a biological information-measuring model by performing multiple linear regression (MLR) on the obtained data, and measuring a biological signal of the body part by using the obtained biological information-measuring model.