To obtain an optimum method and device configuration for observing quantum dots.

In this quantum dot observation method for applying excitation light to a quantum dot and detecting the emission of light at a plurality of different wavelength regions from the quantum dot, the device for executing the quantum dot observation method, where the wavelength band of excitation light can be variably adjusted consists of a light source 11 for generating excitation light for the quantum dot, an illumination optical system 1 for condensing excitation light from the light source 11 and applying the light to a sample which includes the quantum dot, and a detection optical system 2 for detecting emission of light at a plurality of different wavelength regions from the quantum dot. Also, the illumination optical system 1 has a variable filter means 13 for adjusting the wavelength band of the excitation light.