The present invention provides a light guide element, a light guide unit, a backlight apparatus and a light source apparatus. The light guide element is provided for guiding a light flux from a light source into a light guide plate, and the light guide element includes: an incident surface; an emitting surface; a top surface and a base surface, in which one of the top surface and the base surface inclines to the other. The light guide element further includes a structure in a light leakage reducing shape arranged on at least one of the top surface and the base surface, which reduces an amount of light to be emitted from the surfaces of the light guide element excluding the emitting surface.