The invention discloses a refractometer for measuring the distribution of refractive indexes, belonging to the fields of measurement and optics. The refractometer comprises a light source unit, an optical path adjusting unit, a detecting unit and an image collecting and processing unit, wherein the light source unit is used for generating parallel light; the optical path adjusting unit is used foradjusting the size of a parallel light beam according to a set measurement range, and is also used for adjusting the direction of the parallel light beam so as to allow the parallel light beam to perpendicularly enter the detecting unit; the detecting unit comprises a prism and a lens array, the lens array is attached onto one side surface of the prism and used for receiving the parallel light beam from the optical path adjusting unit, and the bottom surface of the prism is attached onto the interface of a to-be-measured object; and the image collecting and processing unit is used for receiving a light spot emitted from the other side surface of the prism, and is also used for image processing of the light spot to obtain the refractive index of the to-be-measured object. The refractometerprovided by the invention has simple and compact structure, can measure the distribution of refractive indexes, and has high measurement precision.