A measuring instrument has a light source for irradiating light including rays of light having the wavelength of excitation light, an objective lens for focusing light irradiated from the light source to a predetermined focusing position, a first mirror for directly reflecting light from the objective lens, a second mirror for reflecting light reflected by the first mirror, the second mirror having an aperture P, and a measuring device for measuring light generated from a sample and having a wavelength different from the wavelength of excitation light, and the sample being arranged between the first mirror and the second mirror, the focusing position of the objective lens being made to agree with the position of the aperture P, and the measuring device being adapted to measure light of a wavelength different from the wavelength of excitation light generated from the sample and passing through the aperture P.