Provided are a layered film defect detection device capable of performing defect detection considering irregularities of optical performance of a phase difference layer constituting the layered film without requiring insertion of a new part into an optical path; and a layered film defect detection method. A defect detection device used for a layered film (11) having a polarizing plate (1) and a phase difference layer (separator (2)) includes: a light source (12) arranged at one side of the film surfaces of the layered film (11), an imaging unit (13) arranged on the other side of the film surface; an inspection polarization filter (15) arranged between the light source (12) and the imaging unit (13); a defect detection unit (14b) for detecting a defect existing on the polarizing plate (1) according to the captured image; and an optical axis adjusting unit (16) for adjusting a relative angle position of the polarization axis (L2) of a polarizing filter (15) and a polarization axis (L1) of a polarizer (2). In the detection device, the relative angle position of the polarizing filter (15) is adjusted within a range of the polarization axis angle x of the polarizing filter satisfying the relationship 0 degrees