A helmet disinfecting device (1) comprises a first area (2) arranged to receive a helmet to be disinfected and a compartment (5) for housing the helmet. The housing compartment (5) comprises a base surface (5a) for receiving the helmet and a top surface (5b) opposite to the base surface at which at least one dispenser nozzle (4) is arranged, provided for dispensing a disinfectant aerosol in the housing compartment (5). The device (1) further comprises a second area (3), different from the first one (2), comprising a tank (10) for disinfectant liquid and an aerosol generator device (11) active on the tank (10), in fluid communication with the dispenser nozzle (4), for generating a disinfectant aerosol. The device (1) further comprises a command and control unit (15) configured to send at least activation (SA) and de-activation (SD) signals to the aerosol generator device (11).