To provide a surface inspection device capable of preventing reduction of the quantity of detected light.

This surface inspection device 1 is equipped with an illumination part for irradiating linearly polarized light using ultraviolet light onto the surface of a wafer having a prescribed repeated pattern, a detection part for detecting a polarized light component whose vibration direction is approximately perpendicular to the linearly polarized light in reflected wave from the surface of the wafer onto which the linearly polarized light is irradiated, and an inspection part for inspecting existence of a defect in the repeated pattern based on the polarized light component detected by the detection part. A polarizing plate 34 for acquiring the linearly polarized light or the polarized light component is disposed in the sealed state to the outside air by a sealing member 36 on an optical path of the illumination part or the inspection part.