A sintered silicon oxide for film vapor deposition having a density of 1.0 to 2.0 g/cm3, three-point flexural strength of at least 50 g/mm2, and a BET specific surface area of 0.1 to 20 m2/g is provided. When this sintered silicon oxide is used for evaporation source of a film, pin holes and other defects of the film caused by the problematic splash phenomenon can be reliably prevented and stable production of a reliable package material having excellent gas barrier property is been enabled. This invention also provides a method for producing such sintered silicon oxide, and this method can be used in a large scale production without requiring any special technology, and therefore, this method is capable of supplying the market with the sintered silicon oxide at reduced cost.