We report the quantitative evaluation of the UV scattering effect on the SO2 emission rate measurement by the compact UV spectrometer system. Plume spectra were obtained simultaneously at three measuring points with different distance to the volcanic plume. The apparent absorbance decreases with increasing distance to the plume and the attenuation becomes stronger at shorter wavelength bands. In addition, the attenuation intensity depends on the SO2 column concentration. The underestimation of the measured absorbance caused by the UV scattering leads to the underestimation of the SO2 emission rate. The attenuation was not significant with any wavelength band (<¿10%) at 0.6 km but was 35--50% with shorter wavelength band at 2.6 km distance. The UV scattering effect on the SO2 emission rate estimation can be evaluated by the comparison of the emission rates calculated with different wavelength bands.