A planar light source includes a large variable width of an irradiation angle of illumination light, a display device having a large variable width of an angle of field that uses the planar light source, a portable terminal device that uses the display device, and a ray direction switching element that is incorporated in the planar light source. A beam direction regulating element (a louver), which controls a direction of light, and a transparent and scattering switching element, which can switch the transparent state and the scattering state according to ON and OFF of an applied voltage, are provided between a backlight and a liquid crystal panel, whereby it is possible to increase a variable width of an irradiation angle of light in the planar light source and increase a variable width of an angle of field of the liquid crystal display device that uses the planar light source.