A light source apparatus capable of being reduced in size and thickness and superior in light combining performance includes a prism sheet unit having two mutually parallel prism surfaces each having a plurality of mutually parallel fine prism rows. The prism rows on the two prism surfaces intersect each other at a predetermined angle in plan view. A plurality of light sources are disposed at the light entrance surface side of the prism sheet unit to emit light so that the light is incident on the light entrance surface of the prism sheet unit at a predetermined angle thereto. The lights from the light sources are combined or color-mixed together by passing through the two prism surfaces, and the resulting combined or color-mixed light is emitted as exiting light.