An exhaust gas purification apparatus disposed in an exhaust passage of an internal combustion engine to purify an exhaust gas discharged from the internal combustion engine, the apparatus comprising: an upstream catalyst section which is disposed on an upstream side of the exhaust passage; a downstream catalyst section which is disposed on a downstream side of the exhaust passage with respect to the upstream catalyst section; and a reducing agent solution supplier that supplies a reducing agent solution for generating ammonia from an upstream of the upstream catalyst section, wherein the upstream catalyst section and the downstream catalyst section each include a SCR catalyst constituted by a zeolite, the SCR catalyst adsorbing ammonia and reducing NOx in the exhaust gas, and a skeleton density, which is defined as the number of TO 4 tetrahedrons (T=Si, Al, etc.) in a crystal which is included in a 1000Å 3 volume of the zeolite, of the SCR catalyst included in the upstream catalyst section is less than a skeleton density of the SCR catalyst included in the downstream catalyst section (A < B), wherein the exhaust gas purification apparatus further comprises: a filter catalyst section disposed on the upstream side of the exhaust passage; and a plurality of honeycomb catalyst sections disposed on the downstream side of the exhaust passage with respect to the filter catalyst section, wherein the upstream catalyst section is provided as the filter catalyst section; and the downstream catalyst section is provided as the honeycomb catalyst section disposed on a downstreammost side of the exhaust passage, among the plurality of the honeycomb catalyst sections. an upstream catalyst section which is disposed on an upstream side of the exhaust passage; a downstream catalyst section which is disposed on a downstream side of the exhaust passage with respect to the upstream catalyst section; and a reducing agent solution supplier that supplies a reducing agent solution for generating ammonia from an upstream of the upstream catalyst section, wherein the upstream catalyst section and the downstream catalyst section each include a SCR catalyst constituted by a zeolite, the SCR catalyst adsorbing ammonia and reducing NOx in the exhaust gas, and a skeleton density, which is defined as the number of TO 4 tetrahedrons (T=Si, Al, etc.) in a crystal which is included in a 1000Å 3 volume of the zeolite, of the SCR catalyst included in the upstream catalyst section is less than a skeleton density of the SCR catalyst included in the downstream catalyst section (A < B), wherein the exhaust gas purification apparatus further comprises: a filter catalyst section disposed on the upstream side of the exhaust passage; and a plurality of honeycomb catalyst sections disposed on the downstream side of the exhaust passage with respect to the filter catalyst section, wherein a filter catalyst section disposed on the upstream side of the exhaust passage; and a plurality of honeycomb catalyst sections disposed on the downstream side of the exhaust passage with respect to the filter catalyst section, wherein the upstream catalyst section is provided as the filter catalyst section; and the downstream catalyst section is provided as the honeycomb catalyst section disposed on a downstreammost side of the exhaust passage, among the plurality of the honeycomb catalyst sections.