A light guide (3) for a surface light source used to constitute a surface light source in combination with a primary light source (1) and guiding light emitted from the primary light source (1). The light guide (3) has a light incident end face (31) on which the light emitted from the primary light source (1) impinges, a light exit face (33) from which guided light exits, and a rear surface (34) on the opposite side. A plurality of prism arrays (34a) extending in a direction traversing the light incident end face (31) are formed on at least one of the light exit face (33) and the rear surface (34), and each prism array (34a) has a plurality of divided top portions (34a1, 34a2) where the top is divided in the cross-section profile thereof in at least a partial region in the extending direction.