The invention provides a temperature measurement apparatus and method, being able to processing substrate with nice accuracy and nice effuciency, comparing with the prior art. The temperature measurement apparatus includes a light source; a first splitter (120) that splits a light beam from light source into a measurement beam and a reference beam; a reference beam reflector (140) that reflects the reference beam; an optical path length adjustor (150) for changing the reference beam optical path length; a second plitter (121) that splits the reflected reference beam from the reference beam reflector (140); a first photodetector (160) that measures an interference between the first reflected reference beam and a reflected measurement beam obtained by the measurement beam reflected from a target object (10); a second photodetector (161) that only measures an intensity of the second reflected reference beam; and a temperature calculation unit (170) calculates a location of the interference by subtracting an output signal of the second photodetector (161) from an output signal of the first photodetector (160).