There is provided an optical coherent tomography device capable of enlarging a measurement range by removing the affect of a folded image. The device includes an optical phase modulator (14) enabling operation amplifiers (17, 18) and a calculation control device (21) to measure a first intensity as a cosine function for the wave number and a second intensity as a sine function or inverse code function for the wave number from the intensity of the output light multiplexed by a third coupler (16). The calculation control device (21) is based on a first intensity set and a second intensity set of the output light by the optical phase modulator (14) measured by the operation amplifiers (17, 18) and the like, so as to suppress generation of a folded image and identify reflection or a backscattering position and a reflection intensity or a back scattering intensity of the measurement light for the irradiation direction of the measurement light in the measurement object.