A tokamak edge plasma significantly absorbs ICRF waves when a cutoff-resonance-cutoff is present in the evanescent region. Two ion component plasmas in a torus are considered although the plasmas are modelled by a slab. The absorption rate Ab is roughly given by M2 for 1 ≫ M2 > S2 and S4 for 1 ≫ S2 > M2, where M = kyℓ and S ≅ kzℓ and ℓ is a scale-length of the order of the plasma minor radius, and ky and kz are the perpendicular and the parallel components of the wave vector. It is noted that M and S become of the order of unity. Since Ab is not very sensitive to the density ratio of the two ion species, a few per cent of impurities may cause significant absorption. As the mass ratio of the two ion species comes close to unity, the triplet forms readily. Therefore, a D-T plasma seems to suffer more easily from this kind of resonance absorption than a D-H plasma.