PROBLEM TO BE SOLVED: To provide an optical interference tomography diagnostic apparatus using wavelength sweeping which, when abnormalities occur on an optical path from a wavelength swept light source to the tip of a probe, can identify the position.SOLUTION: On an optical path from a wavelength swept light source 103 to an imaging core 250 on the tip of a probe 101, a plurality of FBG elements 281 to 285 are provided. Each FBG element possesses a specific characteristic reflecting lights whose wavelengths are out of a wavelength range used for image diagnoses in all wavelength ranges which the wavelength swept light source outputs, and whose wavelengths are different to each other. It is analyzed whether or not the reflected light exists and is determined whether or not the measurement light reaches the FBG elements, and when not reaching, is determined whether or not the measurement light reaches which FBG element.
