PROBLEM TO BE SOLVED: To provide a light-diffusing sheet having anisotropic light-diffusing characteristics and suitable for an illumination device which efficiently and uniformly illuminates a space in a longitudinal direction, the space extending in one direction such as a passageway, by using a spot light source or a light source unit having an array of spot light sources.SOLUTION: A production method of a light-diffusing sheet is provided, which includes: a lamination step of laminating at least one layer of a hard layer 12a on one surface of a heat-shrinking film 11 to produce a laminate sheet 10a; and a rugged pattern formation step of forming a rugged pattern on a surface of the hard layer by heating and shrinking the laminate sheet to corrugate and deform at least the hard layer of the laminate sheet. The laminate sheet is shrunk in such a manner that a 1/10-value diffusion angle of light incident from the surface of the sheet where the hard layer is laminated to the light-diffusion sheet is 5 to 15 d
