Lens sheet manufacturing method

Provided is an extrusion molding manufacturing method for a lens sheet having a resin sheet that is thick and a ridge-shaped lens the aspect ratio of which is high. The extrusion manufacturing method for a lens sheet includes the following: a first step in which a thermoplastic resin (A) and a thermoplastic resin (B) the MFR (according to ISO 1133, a value measured under conditions where the temperature is 230°C and the load is 37.3N) of which is smaller than the thermoplastic resin (A) are formed by extrusion molding, and a molten multi-layer sheet, provided with a first layer that is a surface layer and that comprises the thermoplastic resin (A) and the volume per unit length of which is y (y is a positive number), and an adjacent second layer that comprises the thermoplastic resin (B), is obtained using a mutli-manifold die; and a second step in which n (n is a natural number) ridge-shaped lenses are formed by closely adhering, to a surface formed by the first layer of the molten multi-layer sheets obtained in the first step, a forming die having a plurality of grooves in which the capacity per unit length is x (x is a positive number) which satisfies formula (1). 0.7≤y/nx≤2.0 (1)