To measure a bloodstream speed in a blood vessel and a bloodstream speed of a papilla part by alternatively using a confocal diaphragm and a light shielding diaphragm.

A position of the blood vessel Ev is expressed by a measuring part X1, and a position of a pigmental epithelium existing in the rear is expressed by X2. A light flux is made incident on a mirror 51 from below, and irradiates the measuring part X1 after being reflected in the left direction. The reflected light in the measuring part X1 passes through an opening 52, and passes through a small hole 54 conjugate with the measuring part X1 by a lens 53, and is then received by a photomultiplier 55. The reflected light in the measuring part X2 indicated by a dotted line is formed as an image by the lens 53 similarly to the light flux reflected by the measuring part X1 indicated by a continuous line, and is not made incident on the photomultiplier 55 due to being unable to pass through the small hole 54. When using the confocal diaphragm having the function similar to the small hole 54, influence of scattered reflection from the rear of the blood vessel Ev by the transmitted measuring light is eliminated so that only the reflected light from the blood vessel Ev existing in the specific depth can be received.