A part mounting grommet comprises an outer grommet and an inner grommet inserted into the outer grommet and supported by the outer grommet, and supports a part provided with a mounting member beforehand on a vehicle main body. The outer grommet has a clearance in a radial direction with a mounting hole drilled in the vehicle main body, a first stopper stopped by the outer edge of one side of the mounting hole on one end thereof, and an elastically deformable first latching piece latched with the outer edge of the other side of the mounting hole. The inner grommet has a clearance in the radial direction with the outer grommet, a second stopper which abuts with the first stopper, and an elastically deformable second latching piece latched with the other end of the first stopper. The outer grommet and the inner grommet are respectively movable in the radial direction.