To provide an optical sheet capable of suppressing illuminance unevenness, and improving light use efficiency and a front luminance; a backlight unit using the same; and a display device.

The light control sheet 1 has a substrate part 1b. A light incident face of the substrate part 1b is formed with a large number of minute condenser lenses 1c oriented in one direction, and a light emission face is formed with a large number of minute diffusion lenses 1a oriented in a nearly parallel with the orientation direction of the condenser lens 1c. The condenser lens 1c has an optical structure such that incident light rays are condensed onto the lens surface of the diffusion lens 1a. The diffusion lens 1a has an optical structure for diffusing the condensed light as nearly parallel light advancing along the normal direction of the light control sheet 1. A reflection layer 1d comprises a large number of reflection parts 1d-1 each reflecting light rays incident on a part between the adjacent condenser lenses 1b formed between the adjacent condenser lenses 1b.