A light source apparatus is provided. The light source apparatus includes: a light-emitting portion; a light-guiding plate having the light-emitting portion disposed at a side surface thereof, light beams being emitted from a top surface of the light-guiding plate; and a light path converting sheet above the light-guiding plate, formed of a prism sheet including cylindrical prisms, a cross-section of which is an isosceles triangle. Each of the prisms includes a light incidence plane that forms a first equilateral constituting an apex angle of the isosceles triangle, a reflection plane that forms a base of the isosceles triangle and a light exit plane that forms a second equilateral constituting the apex angle of the isosceles triangle The prism is disposed such that the light incidence plane is approximately perpendicular to a direction of light beams with highest luminous intensity among the light beams emitted from the top surface of the light-guiding plate.