An optical fiber temperature sensor has a sensing part composed of an optical fiber arranged at a temperature measurement point; a light source for injecting a light to the sensing part; a wavelength filter module for branching the Raman scattered light from the back scattered light generated at the sensing part; photoelectric detectors for detecting the Raman scattered light and a signal processing circuit for processing the electric signals from the photoelectric detectors, wherein the light source is a semiconductor laser having a wavelength bandwidth of 0.78 .mu.m; the wavelength filter module has a longer wavelength side band pass filter for transmitting the Stokes light and a shorter wavelength side band pass filter for transmitting the anti-Stokes light; and the longer wavelength side band pass filter and the shorter wavelength side band pass filter do not allow the light having the wavelength band of the semiconductor laser to be transmitted.