An apparatus for blocking ambient air of an electrodeless lighting system comprises: a waveguide including a shaft hole so that a bulb shaft can be penetrated therethrough; a bulb motor mounted on a rear side of the waveguide and connected to a bulb, which is located on a front side of the waveguide, using the bulb shaft for rotating the bulb; and a sealing unit installed between the bulb motor and the waveguide for blocking inflow of ambient air to a direction of the bulb, that is, a sealing structure can be ensured so that the ambient air is not flowed into the light emitting area where the mesh screen is located, and thereby impurities are not flowed into the light emitting area to ensure the clear light emitting conditions, the oxidization of mesh screen can be reduced, and the stability of the lighting apparatus is improved and maintenance cost can be reduced.