A reflection characteristics measurement device, comprising an illumination device that illuminates a to-be-illuminated surface, and a light-receiving mechanism including a mirror or a prism, said illumination device comprising: a surface light source being disposed on a normal line of said to-be-illuminated surface; and a reflection mechanism being provided between said surface light source and said to-be-illuminated surface so as to surround said normal line for reflecting a light emitted from said surface light source toward said to-be-illuminated surface, wherein in said reflection mechanism, a reflection region that reflects said light toward said to-be-illuminated surface and a low-reflection region having a reflection ratio at a time of reflecting said light toward said to-be-illuminated surface lower than said reflection region are alternately disposed along a virtual cylindrical surface surrounding said normal line in a circumferential direction of said virtual cylindrical surface, and three or more reflection regions and three or more low-reflection regions are thereby disposed, with one of said low-reflection regions receiving said light-receiving mechanism, with said mirror or said prism of the light-receiving mechanism located on said normal line; each of said three or more reflection regions is a region having a partially-cylindrical shape to follow said virtual cylindrical surface, and said three or more low-reflection regions are dispersedly disposed to surround said normal line in said circumferential direction, wherein, a plurality of reflection surfaces reflecting said light toward said to-be-illuminated surface are provided in each of said three or more reflection regions, said plurality of reflection surfaces are arranged along said virtual cylindrical surface in said circumferential direction, and said light-receiving mechanism is configured to receive a reflection light generated at a time when said to-be-illuminated surface reflects said light reflected by said reflection mechanism, and to then output a measurement result of said reflection light. said illumination device comprising: a surface light source being disposed on a normal line of said to-be-illuminated surface; and a reflection mechanism being provided between said surface light source and said to-be-illuminated surface so as to surround said normal line for reflecting a light emitted from said surface light source toward said to-be-illuminated surface, wherein in said reflection mechanism, a reflection region that reflects said light toward said to-be-illuminated surface and a low-reflection region having a reflection ratio at a time of reflecting said light toward said to-be-illuminated surface lower than said reflection region are alternately disposed along a virtual cylindrical surface surrounding said normal line in a circumferential direction of said virtual cylindrical surface, and three or more reflection regions and three or more low-reflection regions are thereby disposed, with one of said low-reflection regions receiving said light-receiving mechanism, with said mirror or said prism of the light-receiving mechanism located on said normal line; each of said three or more reflection regions is a region having a partially-cylindrical shape to follow said virtual cylindrical surface, and said three or more low-reflection regions are dispersedly disposed to surround said normal line in said circumferential direction, a surface light source being disposed on a normal line of said to-be-illuminated surface; and a reflection mechanism being provided between said surface light source and said to-be-illuminated surface so as to surround said normal line for reflecting a light emitted from said surface light source toward said to-be-illuminated surface, wherein in said reflection mechanism, a reflection region that reflects said light toward said to-be-illuminated surface and a low-reflection region having a reflection ratio at a time of reflecting said light toward said to-be-illuminated surface lower than said reflection region are alternately disposed along a virtual cylindrical surface surrounding said normal line in a circumferential direction of said virtual cylindrical surface, and three or more reflection regions and three or more low-reflection regions are thereby disposed, with one of said low-reflection regions receiving said light-receiving mechanism, with said mirror or said prism of the light-receiving mechanism located on said normal line; each of said three or more reflection regions is a region having a partially-cylindrical shape to follow said virtual cylindrical surface, and said three or more low-reflection regions are dispersedly disposed to surround said normal line in said circumferential direction, wherein, a plurality of reflection surfaces reflecting said light toward said to-be-illuminated surface are provided in each of said three or more reflection regions, said plurality of reflection surfaces are arranged along said virtual cylindrical surface in said circumferential direction, and said light-receiving mechanism is configured to receive a reflection light generated at a time when said to-be-illuminated surface reflects said light reflected by said reflection mechanism, and to then output a measurement result of said reflection light.