The device for the microbiological analysis of a support adapted to contain microorganisms marked by a fluorophore agent, said agent being adapted to absorb light energy with an absorption spectrum (53) having a crest (53') at a predetermined absorption wavelength (» 2 ) and to release that energy by emitting light with an emission spectrum (54) having a crest (54') at a predetermined emission wavelength (» 3 ) distinct from said absorption wavelength (» 2 ), comprises illuminating means; the spectrum (55) of the excitation light coming from the illuminating means having a crest (55') at a predetermined excitation wavelength (» 1 ) with a predetermined difference between the excitation (» 1 ) and absorption (» 2 ) wavelengths by virtue of which it is made easy to discriminate the light emitted by said fluorophore agent from that coming from the illuminating means.
