A measurement apparatus obtains a reference signal from reference light modulated at a first frequency and a measurement signal from measurement light reflected by a target object modulated at a second frequency along with movement of the target object in addition to the modulation at the first frequency, and processes the reference signal and the measurement signal to measure a position of the target object. Synchronized detection units multiply the measurement signal by a signal synchronized with the reference signal and output signals having the second frequency and harmonic components. Decimation filters filter, at a decimation frequency, the signals output from the synchronized detection units to attenuate the harmonic components.