A device including an optical measuring device and an optical system which can measure the light intensity of the scattered light from the sample and the spatial distribution of the scattered light and which is excellent in the sensitivity is provided. In the device, the image distortion is suppressed by providing such a structure that the light emitted from the first substance is reflected by the ellipsoidal mirror two or more even times before reaching the second substance. The image distortion is suppressed by arranging two ellipsoidal mirrors so that respective one focuses are set to a common focus while remaining other two focuses are arranged on one line so as to be opposite to each other across the common focus, setting the common focus to a blank, arranging a first substance on one of the focuses, and arranging a second substance on the other of the focuses.