Collision-free lifetimes and deactivation rate constants of SO(B(3)Sigma(-), v' = 0, 1, and 2) by collisions with He have been determined. SO(X(3)Sigma(-)) was generated in the photolysis of SO2 at 193 nm (ArF laser) and excited to a single rovibrational level of B(3)Sigma(-) with a pulsed ultraviolet laser. We recorded dispersed fluorescence spectra, and found that 0-12 (350.8 nm), 1-14 (368.5 nm), and 2-17 (401.2 nm) bands are suitable for detecting fluorescence from single vibrational level of interest. Time profiles of wavelength-resolved fluorescence were recorded at various buffer gas pressures (5-165 Torr of He). Deconvolution by the integrated phase plane method derives apparent fluorescence lifetime at a given pressure. Total pressure dependence of fluorescence decay rates leads to collision-free lifetimes and rate constants for deactivation of SO(B(3)Sigma(-), v' = 0, 1, and 2) by collisions with He. Lifetimes of SO((BE-)-E-3) have been determined to be (28 +/- 2) ns (v' = 0), (30 +/- 3) ns (v' = 1), and (27 +/- 4) ns (v' = 2). Rate coefficients for deactivation of SO(B(3)Sigma(-)) by He have been obtained to be (6.3 +/- 0.3) x 10(-12), (3.9 +/- 0.2) x 10(-11), and (1.3 +/-0.2) x 10(-10) in units of cm(3) molecule(-1) s(-1) for v' = 0, 1, and 2, respectively. To the best of our knowledge, deactivation rate constants for v' = 0 and 1 of SO(B(3)Sigma(-)) are measured for the first time in the present study. The large rate coefficient of deactivation by He and vibrational level dependence is explained by predissociation via the C(3)Pi state.