A plurality of backlight blocks are aligned, each block includes light sources and a unit light guide plate for guiding light from the light sources to the side of a liquid crystal panel, unit diffusion patterns are formed in a zigzag alignment on the unit light guide plate and another diffusion pattern is formed on the back of the unit light guide plate. One side of the unit light guide plate is defined as a light entrance surface and LEDs as the light sources are aligned along the light entrance surface to satisfy p≧a≧c where a indicates the size of the unit diffusion pattern in a direction orthogonal to an exit optical axis of the LEDs, c indicates the size of an LED emission surface in the direction of alignment of the LEDs, and p indicates the pitch of alignment of the light sources.