An exhaust gas purification device includes: a wall-flow-structured base material having input-side cells, output-side cells, and a porous partition wall; and a catalyst layer formed inside the partition wall contacting the input-side cells or the output-side cells. The catalyst layer is formed in a region extending from the surface of the partition wall and covering at least 90% of the thickness of the partition wall, and is held by the surfaces of the inside pores of the partition wall in the region. Further, the average filling ratios A, B, and C of the catalyst layer held by pores in respective pore size ranges satisfy a specific relationship.