Abstract: A microwave heating apparatus of a dielectric heating system used in combination with a radiant heat source.A leakage waveguide group is formed by arranging a number of leakage waveguides, each having at least in one side surface thereof an electric wave radiation opening which may be in the form of a long slit; and the same is closed at each electric wave radiation opening thereof with heat resistant non-metal material such as Teflon, glass or the like and is arranged so that a heating medium such as hot air, steam or the like may be passed therethrough.According to this construction, as compared with a conventional microwave heating apparatus of this kind, the heating energy is more sufficiently consumed in an object to be heated, so that the heating speed can be improved and the available space in the heating chamber can be enlarged.