A plane illumination apparatus comprising: an optical device configured to be capable of diffusing coherent light beams from respective points to an entire region of the corresponding areas in an illumination zone and to change an incident direction of the coherent light beams incident on respective points of the illumination zone with time; an irradiation unit configured to irradiate the coherent light beams to the optical device so that the coherent light beams scan a surface of the optical device; and a light guide plate configured to make coherent light beams that are reflected at a surface of the optical device or that have passed through the optical device propagate and to comprise a light take-out surface from which the coherent light beams are taken out to outside, wherein the irradiation unit makes the coherent light beams scan the surface of the optical device by changing propagation directions of the coherent light beams, the light guide plate comprises a light take-out portion configured to take out coherent light beams to outside while making coherent light beams propagate between a first end face on which coherent light beams from the optical device are incident and a second end face that is provided to face the first end face, the illumination zone is provided inside the light take-out portion or along the first end face, or along the second end face, the light take-out surface is a third end face that is connected to the first and second end faces (31a, 31b), the irradiation unit is provided at a rear side of a fourth end face that is an opposite side to the light take-out surface of the light take-out portion; and wherein the irradiation unit comprises: a light source to emit coherent light beams; and a scanning device to make the coherent light beams emitted from the light source perform scanning on a surface of the optical device by changing propagation directions of the coherent light beams. an optical device configured to be capable of diffusing coherent light beams from respective points to an entire region of the corresponding areas in an illumination zone and to change an incident direction of the coherent light beams incident on respective points of the illumination zone with time; an irradiation unit configured to irradiate the coherent light beams to the optical device so that the coherent light beams scan a surface of the optical device; and a light guide plate configured to make coherent light beams that are reflected at a surface of the optical device or that have passed through the optical device propagate and to comprise a light take-out surface from which the coherent light beams are taken out to outside, wherein the irradiation unit makes the coherent light beams scan the surface of the optical device by changing propagation directions of the coherent light beams, the light guide plate comprises a light take-out portion configured to take out coherent light beams to outside while making coherent light beams propagate between a first end face on which coherent light beams from the optical device are incident and a second end face that is provided to face the first end face, the illumination zone is provided inside the light take-out portion or along the first end face, or along the second end face, the light take-out surface is a third end face that is connected to the first and second end faces (31a, 31b), the irradiation unit is provided at a rear side of a fourth end face that is an opposite side to the light take-out surface of the light take-out portion; and wherein the irradiation unit comprises: a light source to emit coherent light beams; and a scanning device to make the coherent light beams emitted from the light source perform scanning on a surface of the optical device by changing propagation directions of the coherent light beams. a light source to emit coherent light beams; and a scanning device to make the coherent light beams emitted from the light source perform scanning on a surface of the optical device by changing propagation directions of the coherent light beams.