PURPOSE: To provide a two-photon excitation microscope which can scan at a high speed and can efficiently utilize light.

CONSTITUTION: The two-photon excitation microscope which is used for observing fluorescence from a sample 6a by simultaneously irradiating the sample 6a with two photons having a wavelength which is twice of that of exciting light used at the time of exciting the sample 6a with a single photon is provided with a laser 1a which can excites the two photons, rotary plate 8 to which the output light of the laser 1a is made incident and which is provided with a plurality of microlenses, dichroic mirror 2a which transmits or reflects light rays from the microlenses and separate the fluorescence generated from the sample 6a, objective lens 5a which condenses the transmitted light or reflected light from the mirror 2a, and image pickup device 10 or eyepiece device to which the light from the mirror 2a is made incident.