PROBLEM TO BE SOLVED: To provide a catalyst carrier composite body having high catalyst reaction efficiency without excessively reducing a flow passage width or excessively increasing a flow passage length.SOLUTION: In a catalyst carrier composite body 1, a plurality of tabular catalyst carrier units 10 are layered, the catalyst carrier unit 10 includes a plurality of flow passage wall face members 20, and an upstream side adjacent catalyst carrier unit 10a provided on the upstream side of a flow-through direction 85 of a treated fluid 80 and a downstream side adjacent catalyst carrier unit 10b provided on the downstream side of the plurality of layered catalyst carrier units 10 have relation wherein an upstream side end part 22 on the upstream side adjacent catalyst carrier unit 10a side of the flow passage wall face members 20 of the downstream side adjacent catalyst carrier unit 10b is positioned inside an upstream flow passage projection region 35 obtained by projecting a section perpendicular to the flow-through direction 85 of a flow passage of the upstream side adjacent catalyst carrier unit a to the downstream side adjacent catalyst carrier unit 10b.
