Origin of the purple color of chromium-containing SnO₂(Cr-SnO₂) was studied mainly by ESCA, ESR and diffuse reflectance spectroscopies. It was found that when the Cr₂O₃ content in Cr-SnO₂ was higher than 1.5wt%, the color of Cr-SnO₂ is not purple but green due to the presence of Cr³⁺ in the aggregate state. ESCA and ESR analyses of the chemical state of chromium in Cr-SnO₂ revealed that Cr⁶⁺, Cr⁵⁺ and Cr³⁺ are minor species when the Cr₂O₃ content in Cr-SnO₂ was about 0.2wt%. Addition of Al³⁺ or Sb⁵⁺ to Cr-SnO₂ gave rise to absorption bands at about 450 and 600nm or 470 and 650nm respectively, indicating that Cr⁵⁺ and Cr³⁺ in Cr-SnO₂ are not responsible for the purple color (570nm). Consequently, the broad absorption band at 570nm was considered to be produced by Cr⁴⁺.