This surface defect detection method is for optically detecting a surface defect of a steel pipe (P), and includes an irradiation step for irradiating illumination light beams (L) from different directions onto the same region under inspection on a steel pipe (P) using two distinguishable light sources (2a, 2b) and a detection step for acquiring images of the reflected light of the light beams (L) and detecting a surface defect on the region under inspection by carrying out subtraction processing using the acquired images. As a result, it is possible to accurately distinguish scales and benign patterns from surface defects.