A vehicular antenna device includes an antenna portion having an antenna element, and a frame accommodating a heat generation member. The vehicular antenna device is configured to be attached to an attachment portion of a vehicle. The frame includes a first space portion having a cylindrical shape and defining a first space, the first space portion being exposed to an outside air in a condition where the vehicular antenna device is attached to the vehicle. The heat generation member is located along a second surface of the frame that is a reverse side of a first surface defining the first space. The antenna portion is detachable from the frame.