A temperature measuring apparatus includes a light source, a first splitter, a second splitter, a reference beam reflector, an optical path length adjuster, a reference beam transmitting member, a first to an nth measuring beam transmitting member and a photodetector. The temperature measuring apparatus further includes an attenuator that attenuates the reference beam reflected from the reference beam reflector to thereby make an intensity thereof closer to an intensity of the measurement beam reflected from the temperature measurement object.