The linear light source apparatus includes an elongated rectangular wiring substrate; a plurality of light-emitting devices which are aligned on a straight line on the top surface of the wiring substrate; reflectors provided on the top surface such that each reflector corresponds to one light-emitting device; a sealing resin portion which seals each of the light-emitting devices; and a heat radiation sheet provided on the bottom surface of the wiring substrate. A plurality of grooves are provided on the bottom surface of the substrate. Each groove is formed so as to have a line shape and to extend in a lateral direction of the wiring substrate. Each of the grooves is located between adjacent light-emitting devices. The heat radiation sheet is provided on the entire bottom surface of the wiring substrate.