The present invention provides: an oxide sintered body having superior manufacturing stability, film stability, discharge stability, and mechanical strength; a process for manufacturing the same; and an oxide film obtained by using the oxide sintered body and having an intermediate refractive index. The oxide sintered body comprising In and Si, wherein a Si content is 0.65 to 1.75 in Si/In atomic ratio, a relative density is 90% or more, and a bending strength is 90 N/mm2 or more, is manufactured, and the oxide film with refractive index of 1.70 to 1.90 by a sputtering process using the oxide sintered body is manufactured.