It is necessary to compensate an intensity variance of optical signals in optical networks for accurate data reception and accurate signal processing. In future packet-switching networks, it is feared that a large intensity variance of optical signals in optical packets would be caused by such a clock recovery, and a gain transient of EDFA, and so on. To cope with the large intensity variance of optical signals in optical packets, we propose a wide dynamic range all-optical intensity equalizer based on an effective control of spectral modulation induced by self-phase modulation (SPM) using super-Gaussian signals. We have calculated the spectra after SPM effects for super-Gaussian signals with changing the intensities of input optical signals. As the results, we have successfully realized appropriate control of spectral modulation so that the magnitudes around centre wavelength components might be approximately equivalent for input intensities over a wide range. By using computer simulation, we have verified the function of proposed intensity equalizer by adopting the calculated magnitude-equivalence after SPM. We confirmed a remarkable wide dynamic range and a high-accuracy intensity equalizing effect of the proposed method.