Changes in chemical states of amorphous carbon film during ethylene (C2H4) plasma in the floating potential were investigated with multiple-internal-reflection infrared absorption spectroscopy (MIR-IRAS) and deposition rates. IRAS spectra showed that the peaks due to the sp(3)-CHX were observed, but no peaks due to sp(2)-CHX were observed. The deposition rate due to ethylene plasma was nearly twice that due to methane plasma, in the same way that the number of carbons in an ethylene molecule is twice as that in a methane molecule. It is suggested that the film growth due to ethylene plasma is the same manner of that due to methane plasma; the plasma-generated hydrocarbon species such as C2H3 and C2H5, which are generated in ethylene plasma, are adsorbed on dangling bonds that are generated by hydrogen abstraction from the deposited film surface. As a result, the deposited film is composed of sp(3)-hydrocarbon components.