A composition for purifying an ozone-containing gas comprising activated carbon, in which the percentage of the volume of pores having a pore diameter of 0.4-0.8 nm in the volume of pores having a pore diameter of 0.4-2.0 nm is 75% or more, and an ozone decomposition catalyst powder is disclosed. Also disclosed is a filter for purifying an ozone-containing exhaust gas comprising activated carbon powder, in which the percentage of the volume of pores having a pore diameter of 0.4-0.8 nm in the volume of pores having a pore diameter of 0.4-2.0 nm is 75% or more, and an ozone decomposition catalyst powder carried on a fiber supporting body. The composition and filter of the present invention can remarkably reduce the content of ozone and volatile organic compounds in ozone-containing exhaust gas from printers.