First and second polarizing plates are placed to be crossed nicols across a film to be inspected. A light source projects light toward the film through the first polarizing plate. Alight receiver receives the light transmitted through the film and the second polarizing plate. When .theta.1 represents an angle formed between an optical axis of the light receiver and a normal line that is perpendicular to the film surface, and .theta.2 represents a rotational angle formed between the optical axis and a reference line that is orthogonal to a slow axis of the film, the light receiver is positioned to satisfy the following conditions:15.degree..ltoreq..theta.1.ltoreq.35.degree., 20.degree..ltoreq..theta.2.ltoreq.60.degree..