A laser microscope is provided in which a beam splitter extracts a part of a laser light of two wavelengths .lamda.1=488 nm and .lamda.2=514.5 nm, a prism spectrally resolves the laser light of the two wavelengths .lamda.1 and .lamda.2, a two-split photodiode detects intensities of two lines spectrally resolved in this manner, and a controller controls an acousto-optical tunable filter (AOTF) fixed to an output end of an argon laser based on a detection signal outputted from the two-split photodiode so that respective light intensities of both lines of wavelengths .lamda.1 and .lamda.2 become constant.