To efficiently obtain a powder having a wide specific surface area and a small primary particle diameter and high electroconductivity at a low cost.

This electroconductive oxide powder has a crystal structure of an In3SbO7-based double oxide consisting essentially of indium and antimony in an atomic ratio of In:Sb=3: (1+X) (with the proviso that X is -0.3≤X≤0.3), ≥5 m2/g specific surface area (BET value) and 5-1,000 nm average particle diameter of primary particles.