A microscope apparatus comprising: a scanner including a pair of galvanometer mirrors that is configured to perform scanning of illumination light emitted from a light source on a specimen in two directions intersecting each other; an objective lens that is configured to collect fluorescence produced in the specimen; one of a prism and a diffraction grating that is configured to disperse the fluorescence collected by the objective lens into spectral components; a light detector that has a plurality of cells for detecting the spectral components obtained through the dispersion performed by the one of the prism and the diffraction grating, wherein sensitivities of each of the plurality of the cells are individually adjustable by individually controlling a voltage which is applied to each of the plurality of cells and used to adjust the sensitivities of each of the plurality of cells; a display, wherein a graphical user interface is displayed on the display, the graphical user interface being configured to receive input from a user for selecting a group of cells from among the plurality of cells of the light detector; and a computer that includes: a grouping control section that is configured to group the plurality of cells of the light detector into a used group and an unused group according to the group of cells selected based on the input by the user; and a sensitivity control section that is, by individually controlling the voltage which is applied to each of the plurality of cells, configured to turn off sensitivities of cells that are grouped into the unused group by the grouping control section or reduce the sensitivities thereof with respect to sensitivities of cells that are grouped into the used group, wherein the scanner further comprises a signal output section for sending, to the sensitivity control section, a first synchronization signal that is synchronized with a timing of scanning by one of the pair of galvanometer mirrors in a first scanning direction and a second synchronization signal that is synchronized with a timing of scanning by the other of the pair of galvanometer mirrors in a second scanning direction; and wherein the sensitivity control section is configured to individually control the sensitivities of each of the cells of the unused group by individually controlling the voltage which is applied to each of the plurality of cells, in synchronization with the first synchronization signal or the second synchronization signal, which is sent by the signal output section. a scanner including a pair of galvanometer mirrors that is configured to perform scanning of illumination light emitted from a light source on a specimen in two directions intersecting each other; an objective lens that is configured to collect fluorescence produced in the specimen; one of a prism and a diffraction grating that is configured to disperse the fluorescence collected by the objective lens into spectral components; a light detector that has a plurality of cells for detecting the spectral components obtained through the dispersion performed by the one of the prism and the diffraction grating, wherein sensitivities of each of the plurality of the cells are individually adjustable by individually controlling a voltage which is applied to each of the plurality of cells and used to adjust the sensitivities of each of the plurality of cells; a display, wherein a graphical user interface is displayed on the display, the graphical user interface being configured to receive input from a user for selecting a group of cells from among the plurality of cells of the light detector; and a computer that includes: a grouping control section that is configured to group the plurality of cells of the light detector into a used group and an unused group according to the group of cells selected based on the input by the user; and a sensitivity control section that is, by individually controlling the voltage which is applied to each of the plurality of cells, configured to turn off sensitivities of cells that are grouped into the unused group by the grouping control section or reduce the sensitivities thereof with respect to sensitivities of cells that are grouped into the used group, wherein the scanner further comprises a signal output section for sending, to the sensitivity control section, a first synchronization signal that is synchronized with a timing of scanning by one of the pair of galvanometer mirrors in a first scanning direction and a second synchronization signal that is synchronized with a timing of scanning by the other of the pair of galvanometer mirrors in a second scanning direction; and wherein the sensitivity control section is configured to individually control the sensitivities of each of the cells of the unused group by individually controlling the voltage which is applied to each of the plurality of cells, in synchronization with the first synchronization signal or the second synchronization signal, which is sent by the signal output section.