A first luminous flux emitted from the front end face of a LD is reflected by a mirror to be made incident on a detection point on the surface of a measuring object, and a second luminous flux emitted from the rear end face of the LD is reflected by another mirror to be made incident on the detection point. Scattered light from the first detection point is received in a photodiode. A signal processing circuit part calculates the frequency shift quantity of the scattered light based on output from the photodiode. As a result, a velocimeter is provided which detects the moving speed of a measuring object highly precisely.