Light guide plate, surface light source device, transmission-type image display device

Provided is a light guide panel, a surface light source device and a transmission image display device. The light guide panel is arranged at the back surface side of a prism plate. The prism plate is provided with a plurality of prism units arranged on a surface in row, and each prism unit extends in one direction. The light guide panel comprises: a main body which has a first surface and a second surface opposite to each other and an incidence surface intersecting with the first surface and the second surface; and a plurality of lens units formed on the second surface. Each lens unit has an external shape that enables the value greater than 1.055%, wherein the value is obtained by multiplying the ratio of the luminous flux of light emitted to a preset direction from a point on the first surface to the luminous flux of light emitted to all directions from the point, by the ratio of the amount of light from the first surface and the amount of light incoming to the incidence surface and the ratio is as light em