A mobile type exhaust gas purification apparatus comprising an oxidation catalyst comprising a noble metal component for oxidizing nitrogen oxides in an exhaust gas discharged from a diesel engine, a reducing agent spraying means for supplying the reducing agent selected from a urea component or an ammonia component, and a selective reduction catalyst not comprising a noble metal for removing by reduction nitrogen oxides (NO x) by contacting with the reducing agent, in this order from the upstream side of an exhaust gas passage, characterized in that activity of the selective reduction catalyst is maintained by setting that the noble metal component of the oxidation catalyst comprises platinum and palladium, and ratio of platinum particles existing alone is 20% or less, and by suppressing volatilization of platinum from the oxidation catalyst, even when catalyst bed temperature increases up to 900°C, wherein the exhaust gas purification apparatus is characterized by further arranging a catalyzed combustion filter comprising the noble metal component for removing particulate components in exhaust gas by combustion (oxidation), at the backward of the oxidation catalyst and at the forward of the reducing agent spraying means, and characterized in that activity of the selective reduction catalyst is maintained by setting that the noble metal component of the catalyzed combustion filter comprises platinum and palladium, and ratio of platinum particles existing alone is 3% or less, so as to suppress volatilization of platinum from the catalyzed combustion filter, even when catalyst bed temperature increases up to 900°C, wherein the exhaust gas purification apparatus is characterized in that the catalyzed combustion filter has a ratio of platinum and palladium of 1: 1 to 11: 4, in weight equivalent, and wherein the ratio of platinum particles existing alone is determined in accordance with the method defined in the description. activity of the selective reduction catalyst is maintained by setting that the noble metal component of the oxidation catalyst comprises platinum and palladium, and ratio of platinum particles existing alone is 20% or less, and by suppressing volatilization of platinum from the oxidation catalyst, even when catalyst bed temperature increases up to 900°C, wherein the exhaust gas purification apparatus is characterized by further arranging a catalyzed combustion filter comprising the noble metal component for removing particulate components in exhaust gas by combustion (oxidation), at the backward of the oxidation catalyst and at the forward of the reducing agent spraying means, and characterized in that activity of the selective reduction catalyst is maintained by setting that the noble metal component of the catalyzed combustion filter comprises platinum and palladium, and ratio of platinum particles existing alone is 3% or less, so as to suppress volatilization of platinum from the catalyzed combustion filter, even when catalyst bed temperature increases up to 900°C, wherein the exhaust gas purification apparatus is characterized in that the catalyzed combustion filter has a ratio of platinum and palladium of 1: 1 to 11: 4, in weight equivalent, and wherein the ratio of platinum particles existing alone is determined in accordance with the method defined in the description.