To provide an optical sheet preventing chipping or collapse of a control element due to friction with overlay and underlay sheets during transportation or being used as assembled in a backlight, and having excellent shape retaining property which is advantageous for obtaining a sharp display image, and to provide a backlight unit for a display and a display device.

The optical sheet 24 comprises a base sheet 22, a control element, and a reflection layer 23. The control element is provided on an exit face 22B of the base sheet 22 and controls at least one of the direction, color, range and luminance distribution of light when the incident light to an incident face 22A exits; and the control element is a lens 21 in an embodiment of the present invention. The light reflection layer 23 is provided on the incident face 22A of the base sheet 22 and comprises a light reflecting part 23A and a light transmitting part 23B. The Young's modulus of the control element ranges from 0.2 to 3 gpa at normal temperature (17 to 27C).