A radiation imaging apparatus discriminates a light exposure field of visible light regardless of the color of the clothes (gown) of a subject. The apparatus for the X-ray imaging apparatus has an adjustable exposure field and a color sensor mounted to the underside of a collimator detects a color of the clothes (gown) worn by the subject on the table. Each light amount of a first LED that emits a red light, a second LED that emits a green light and a third LED that emits a blue light and a fourth LED that emits a white light is individually adjusted based on the color of the clothes worn by the subject, which the color sensor discriminates.
