A ventilation fan includes a housing having an opening, a grille structure positioned to cover the opening, a fan module provided in the housing and a function module. The grille structure includes a base defining an outlet, and a grille support spaced apart from the base and connected by the connecting columns A radial inlet is formed between the base and the grille support is in communication with the outlet. The base includes a holder having a holding opening axially downward and faced away from the housing. The function module is disposed within the holder through the holding opening.