In order to generate an optical coherence tomogram extending to a deeper region than a tomogram prescribed by a light source having a clock optical interferometer, an OCT device (1) is provided with: a light source (11) having a clock optical interferometer for outputting laser light and generating a clock signal, the light source (11) being adjusted so that a clock signal can be outputted having a second frequency equal to or lower than a first frequency prescribed for a clock signal used in measuring an image at a first depth a detector (23) for detecting an interference light signal as information of the inside of a subject a multiplier (90) for performing high-frequency conversion of the clock signal outputted from the light source and generating a clock signal having a third frequency higher than the first frequency an AD conversion circuit (51) for converting the signal detected by the detector to a digital signal using the clock signal having the third frequency as a sampling reference, and extracting the digital signal so that the wave numbers of the interference light are equally spaced and a control device (100) for performing image processing of the digital signal and outputting an optical coherence tomogram of the subject to a display device (54).
