Abstract: A method for manufacturing a silica glass block is provided in which, by markedly reducing the bubbles within the silica glass block, the quality of a silica glass block can be improved, contamination of the silica glass block can be prevented, and the yield of the silica glass block can be improved. The method comprises preparing a natural or synthetic silica raw material powder, packing the silica raw material powder into a glass fusing furnace, preheat treating the silica raw material powder packed into the fusing furnace, heating and fusing the heat preheat-treated silica raw material powder, and cooling a silica glass melt fused in the fusing furnace. The silica raw material powder packed into the fusing furnace is closely packed in the packing step, and an evacuation and a rare gas or H2 gas introduction treatment is performed in the preheat treating step.