PURPOSE: To measure easily and accurately road-surface reflection characteristics by utilizing the brigtness and horizontal illuminance of a road surface measurement part by natural light passed through a hemispherical dome of a light diffusing material.

CONSTITUTION: The road exposure measurement part P covered with a nonreflective material 7 except at the hemispherical dome 6 made of the light diffusing member is irradiated with natural light through the dome, and the brightness and horizontal illuminance of the measurement part P detected by a luminance meter photodetection part 8 and an illuminance meter photodetection part 11 respectively are processed by subtraction to measure the reflection characteristics of the measurement part P. This natural light is utilized to the reflection characteristics of a road surface easily and accurately without using a light source, stabilized power source, grid, etc.