The relationship between average grain size on the surface of SnO<inf>2</inf>transparent conductive film and conversion efficiency of the a-Si:H solar cell was investigated. a-Si:H solar cells were fabricated on SnO<inf>2</inf>/glass substrates with various grain sizes. The cell structure was glass/p(SiC)-i-n/Al and the effective cell area was 4 × 10<sup>-2</sup>cm<sup>2</sup>. The reflectivity from the glass substrate was reduced to about 7 percent with increasing the grain size from 0.1 to 0.8µm, and the short-circuit current was inceased from 12 to 14mA/cm<sup>2</sup>. A 7.9 percent of conversion efficiency was achieved using milky SnO<inf>2</inf>film of 0.4-µm average grain size at AM-100mW/cm<sup>2</sup>.