Method for manufacturing polarizing plate with anti-reflection layer

Provided is a method for manufacturing a polarizing plate with an anti-reflection layer, the method being capable of maintaining uniform characteristics of reflected light. The manufacturing method comprises a step Sa and a step Sb. In step Sa, an antireflection layer comprising two or more layers of thin films is formed on one main surface side of a thin film substrate (10). In step Sb, at least one layer constituting the anti-reflection layer is formed into a film, and then the film is irradiated with visible light and reflected light is detected. The film substrate (10) has a first protective film (11), a first adhesive layer (12), a polarizer (13), a second adhesive layer (14), and a second protective film (15) in this order. The distance (D1) between the first protective film (11) and the second protective film (15) in at least a portion of a portion (P) extending from both ends of the polarizer (13) in the width direction is narrower than the distance (D2) between the first protective film (11) and the