An optical coherence tomography apparatus includes: an OCT light source; a first light splitter configured to split an optical path into a first measurement optical path and a reference optical path; a light guide optical system including a second light splitter, configured to guide the measurement light to a test substance through the second light splitter, the second light splitter splitting the reflected light into the first and second measurement optical paths; a detection optical system detecting first interference between the reflected light having passed through the first measurement optical path and the reference light, and second interference between the reflected light having passed through the second measurement optical path and the reference light; and a calculation controller processing an output signal which is output from the detection optical system to obtain OCT data regarding the test substance.