A surface inspection apparatus includes units illuminating repetitive patterns formed on a surface of a suspected substance and measuring a variation in an intensity of regular reflection light caused by a change in shapes of the repetitive patterns, units illuminating the repetitive patterns with linearly polarized light, setting an angle formed between a repetitive direction of the repetitive patterns and a direction of a plane of vibration of the linearly polarized light at a tilt angle, and measuring a variation in a polarized state of the regular reflection light caused by the change in the shapes of the repetitive patterns, and a unit detecting a defect of the repetitive patterns based on the variation in the intensity and the variation in the polarized state of the regular reflection light.