To prepare relatively large-sized sintered compact by CP method and casting method by adding at least one kind of Al, Si, Nb, Ta and Y in specific amounts to SnO2-based powder and sintering the resultant SnO2-based mixed powder at a specific temperature in atmosphere, etc., to provide sintered compact in which specific resistance is specified.

At least one kind of Al, Si, Nb, Ta and Y is added to an SnO2- based powder so that the total amount becomes ≤20 wt.%, further preferably ≤6 wt.% expressed in terms of oxide. The SnO2-based mixed powder is formed and sintered at ≥1,300°C, preferably at 1,450°C for about 1-30 hr, preferably about 2-10 hr in the air atmosphere or oxygen atmosphere to prepare a material for thin film formation comprising an SnO2-based sintered compact having ≤1×107 Ω.cm and free from scattering of composition. A sintered compact used as sputtering target is obtained from the material and surface roughness of the sintered compact is preferably about 0.1-6.0 μm.