A backlight unit in a head-up display apparatus according to the present disclosure includes A plurality of light sources configured to emit light; a plurality of primary light collectors configured to collect the light emitted by the plurality of light sources to transmit, refract, or reflect the collected light; and a secondary light collector configured to recollect the light which is collected by the plurality of primary light collectors. At this point, an optical axis of one among the plurality of light sources, the plurality of primary light collectors, and the secondary light collector is disposed to be different from the other two.