PURPOSE: To provide a light-guiding plate for a surface light source device, with which high brightness can be obtained, ragning over the entire surface, in an boundlessly uniform condition.

CONSTITUTION: In a light-guiding plate for a surface light source, a line light source 41 is arranged at a light-incidenting surface at least one end of a light-guiding plate 1, in which a reflecting layer 11 is formed on one surface while the other surface serves as a light emitting surface, and the light from the line light source 41 is transmitted to the inside of the light-guiding plate 1 so that the light is irregularly reflected by the reflecting layer 11 and emitted from a light emitting plane 21. In the light- guiding plate, if a cutting blade 31 is moved on a reflecting layer forming surface of the light-guiding plate 1, pressing the refecting layer forming surface by a cutting blade 31, with the rake angle of the blade 31 kept at negative, the forming surface of the reflecting layer 11 is crushed, because the force of the blade 31 exceeds the elastic limit of the layer 11. With this, since hole-like recessed parts 12, whose depth and width are random, are formed continuously. By forming recessed part lines 13, in which the recessed parts 12 are arranged continuously, the reflecting layer 11 can be formed.