PURPOSE: To obtain a compact spectrophotometer, by combining optical fiber and a spectroscope part having approximately the same outer diameter as said optical fiber.

CONSTITUTION: Luminous flux from a light source 1 is transmitted to a sample A through an optical fiber 8a for incident light. The light is reflected by the sample A and made incident on an optical fiber 8b for the reflected light. A spectroscope part 10 is connected to the optical fiber 8b. The light is divided by a fiber grating 9 with a diffraction grating in the spectroscope part 10 and detected by a detector 11. Thus the reflected spectrum from the sample A is measured.