Tin oxide monolith was prepared by a sol-gel process using inorganic salt as a starting material. The tin oxide prepared had no aggregations visible to the naked eye and was very transparent in the visible wavelength even after heating in air at 600 degrees C. It was confirmed from X-ray diffraction results that the crystal structure of the tin oxide was of the rutile type. The crystal size changed from 1.4 nm to 23.5 nm as the heating temperature increased from room temperature to 700 degrees C, indicating a possibility to control the crystal size.