An exhaust gas catalyst comprising: a base material having a first end surface for use as an exhaust gas inflow side, a second end surface for use as an exhaust gas outflow side, and a plurality of inner wall surfaces formed by a plurality of through holes penetrating therethrough from the first end surface to the second end surface; and a plurality of catalyst layers formed on the plurality of inner wall surfaces, respectively, wherein: each of the through holes has a central axis; each of the catalyst layers is sectioned into a first region extending from the first end surface toward the second end surface by a predetermined distance, a second region extending from the second end surface toward the first end surface by a predetermined distance, and a third region placed between the first region and the second region; and the catalyst layer is formed such that a distance from the central axis of the through hole to an inner surface of the catalyst layer in the first region of the catalyst layer is smaller than a distance from the central axis of the through hole to the inner surface of the catalyst layer in the third region of the catalyst layer, but larger than a distance from the central axis of the through hole to the inner surface of the catalyst layer in the second region of the catalyst layer; wherein: the third region of the catalyst layer is closer to the first end surface side than to the second end surface side and is recessed toward the base material relative to the first region and the second region of the catalyst layer so that a recessed portion is formed. a base material having a first end surface for use as an exhaust gas inflow side, a second end surface for use as an exhaust gas outflow side, and a plurality of inner wall surfaces formed by a plurality of through holes penetrating therethrough from the first end surface to the second end surface; and a plurality of catalyst layers formed on the plurality of inner wall surfaces, respectively, wherein: each of the through holes has a central axis; each of the catalyst layers is sectioned into a first region extending from the first end surface toward the second end surface by a predetermined distance, a second region extending from the second end surface toward the first end surface by a predetermined distance, and a third region placed between the first region and the second region; and the catalyst layer is formed such that a distance from the central axis of the through hole to an inner surface of the catalyst layer in the first region of the catalyst layer is smaller than a distance from the central axis of the through hole to the inner surface of the catalyst layer in the third region of the catalyst layer, but larger than a distance from the central axis of the through hole to the inner surface of the catalyst layer in the second region of the catalyst layer; wherein: the third region of the catalyst layer is closer to the first end surface side than to the second end surface side and is recessed toward the base material relative to the first region and the second region of the catalyst layer so that a recessed portion is formed. each of the through holes has a central axis; each of the catalyst layers is sectioned into a first region extending from the first end surface toward the second end surface by a predetermined distance, a second region extending from the second end surface toward the first end surface by a predetermined distance, and a third region placed between the first region and the second region; and the catalyst layer is formed such that a distance from the central axis of the through hole to an inner surface of the catalyst layer in the first region of the catalyst layer is smaller than a distance from the central axis of the through hole to the inner surface of the catalyst layer in the third region of the catalyst layer, but larger than a distance from the central axis of the through hole to the inner surface of the catalyst layer in the second region of the catalyst layer; wherein: the third region of the catalyst layer is closer to the first end surface side than to the second end surface side and is recessed toward the base material relative to the first region and the second region of the catalyst layer so that a recessed portion is formed.