To obtain a planar light source which is free from brightness variations or chromaticity variations by using a point light source having a high directivity for emitted light, and to provide a liquid crystal display device capable of obtaining superior display characteristics by using this planar light source device. A planar light source device having an opening in the upper surface comprises a hollow box, a diffusion plate disposed in the opening, a reflecting plate disposed on the bottom of the hollow region of the box, and a plurality of point light sources disposed in a row along at least one side surface of the box. This planar light sources device is characterized by including a refracting element disposed parallel to the row of point light sources and between the point light sources and the hollow region for refracting the light from the point light sources, whereby the light at an incident angle at which the brightness is greatest in the luminous intensity distribution of the light radiated to the irradiation subject surface of the refracting element is refracted to the bottom surface of the box by the refracting element.