Far-infrared magneto-optical studies were performed on α'-NaV 2 O 5 up to 15T. Magnetic absorption modes were observed at 68, 106 and 124cm - 1 below the critical temperature, T C =34K, in E c configuration, and they exhibit softening towards T C . Neither shifting nor broadening of these modes was observed in the presence of the magnetic field up to 15T, which suggests that these modes are caused by the excitation to the magnetic bound states. Besides the sharp absorption modes, a broad absorption band was observed on the spectra of E c. Its oscillator strength shows an anomalous decrease at T C , which would be related to charge disproportion.