Abstract: A metal carrier includes a core (3) having a thinned film containing a metal catalyst. The core includes a first metal sheet (1) corrugated and having a crest with a first radius (R). The core includes a second metal sheet (2) flattened or corrugated smaller in corrugation height than the first metal sheet, The first and second metal sheets are stacked on each other to be wound up. The crest and second metal sheet are joined to each other, having a joint therebetween. A fillet of the catalyst is formed between the joint, the first metal sheet, and the second metal sheet, having an arced surface of a second radius (r) extending between the first and second metal sheets. The first radius is set substantially equal to the second radius.