<；P>；PROBLEM TO BE SOLVED: To provide a plant growing method capable of supplying light suitable for growth of a plant by making effective use of natural light, and an optical member for optical modification used for plant growing material. <；P>；SOLUTION: A plant growing film 1 is formed, by arranging semicircular convex-lens-like projections 3 whose radius is 0.5 mm or more and 3 mm or less on a surface 2a of a light transmissive film 2. The convex-lens-like projections 3 are formed of resin material, containing fluorescent dye at content of 0.02 wt.% or more and 1.0 wt.% or less, and an area ratio of a light-receiving surface (convex curved surface 3a) to a light-emitting surface (flat surface 3b) of each of the convex-lens-like projections 3 is set to 140% or more. By appropriately setting the shape, the dimensions and arrangement pattern of the convex-lens-like projection 3 or the content of the fluorescent dye forming the convex-lens-like projection 3, the natural light whose R/B is about 0.6 usually is modified to modified light whose R/B is about 1.5 to 5 by making the natural light pass through the plant growing film 1. <；P>；COPYRIGHT: (C)2011,JPO&INPIT
