Single- and double-photoionization processes of sulfur dioxide (SO2) have been studied in the photon energy region of 37-120 eV by use of time-of-flight mass spectrometry and the photoion-photoion-coincidence method together with synchrotron radiation. The single- and double-photoionization cross sections of SO2 are determined. Ion branching ratios and the partial cross sections for the individual ions, respectively, produced from the parent SO2+ and SO22+ ions are determined separately at excitation energies where the molecular and dissociative single- and double-photoionization processes occur simultaneously, thus enabling more detailed study of the dissociation processes of the parent SO2+ and SO22+ ions.