An optical tomographic imaging method of picking up a cross-sectional image of an object comprises scanning a predetermined region of the object with spots of a plurality of measurement lights in the same direction so as to irradiate different positions of the object with different spots, detecting interference signals formed by the plurality of return lights reflected or scattered by the object and a plurality of corresponding reference lights reflected by a reference mirror, and executing an arithmetic process on the detected interference signals based on a displacement amount between the different spot positions using interference signals corresponding to at least two of the spots out of the respective interference signals. The region to be scanned has a length smaller than the sum of diameters of the spots in a direction perpendicular to the scanning direction.