A glass substrate was pretreated by thermal and chemical treatments with fluoride solution and molten potassium salt. Thin tin oxide film was prepared on it by vacuum deposition of metallic tin followed by oxidation with air. The sheet resistivity of tin oxide film deposited was found to decrease by the pretreatment with fluoride. The film was composed of round particles that closely coalesced with each other and the sizes of them were affected by the pretreatment of substrate, resulting in the change of the electroconductivity. The effects of the pretreatments were compared with previous results on the same pretreatments for tin oxide film prepared by chemical vapor deposition.