PURPOSE: To reduce a burden on a testee during a measurement without dazzling the subject.

CONSTITUTION: Power of a halogen lamp 11 for measuring the diameter of a blood vessel is supplied from a power source 34 for measurement when measuring and from a power source 35 for alignment through a selector 36 when aligning. The power source 35 for alignment is allowed to change an output current value with a varying mechanism 37, and hence, an inspecting person can adjust the quantity of illumination light in alignment to a desired value according to a request from the testee or the like. An ND filter 42 is arranged in front of a laser light source 17 and the ND filter 42 is inserted into or retreated from an optical system with a solenoid 41. In the judgement in alignment or measurement, identification is performed depending on the operation state of a measuring start switch 38.