An apparatus detects fluorescence. The apparatus, also known as a fluorescence scanner, includes an image detector, which is embodied for detecting image data in the wavelength range of fluorescent light, and an excitation light source, which is embodied for generating light in a wavelength range suitable for exciting the fluorescence. The apparatus has a guide beam projector, which is embodied for generating a guide beam from light in the visible wavelength range. The guide beam is aimed such that a projection of the guide beam, a region that is detectable by the image detector is displayed. The guide beam allows exact viewing of a body region to be examined possible for the surgeon, which is not possible on the basis only of the light for exciting a fluorescence, at least whenever the excitation light is in the non-visible wavelength range, such as IR or NIR, or is generated directly during the recording of the fluorescence image.