Wrinkles on polymer film as surface defect are inspected. The film is transported on an inspecting surface having a color for absorbing light. A dot pattern having dots on a transparent test chart sheet, facing the film, is photographed by image pickup upon reflection of the dot pattern on the film positioned on the inspecting surface. A length of the dots being photographed is measured according to image data, to obtain length information of 1-5. A length data table of the dots is created by arranging the length information of 1-5 at locations of the dots. Occurrence of a wrinkle is determined at one of the locations if a difference between the dots occurs in the length information of 1-5 in the length data table. To a rear of the test chart sheet, inspecting light is applied, passes through, and becomes incident upon the film.