We have proposed a method for non-invasively measuring the temperature changes of water in a micro-region using near infrared (NIR) light. The goal of this study is to measure the temperature changes of biological cells or tissues. This method is on the basis of the phenomenon that the NIR absorption spectrum of water depends on temperature. Absorbance spectra in the wavelength range of 1300-2000nm of water with a thickness of 100 and 500μm were measured by a micro-spectrometer. The measured spectra with temperature-dependence were calibrated using a regression analysis. The standard error of calibration was 0.30℃ for 100μm-thickness.