A separator for a fuel cell, includes a separator plate provided with a flow path groove group through which the reaction gas flows. The flow path groove group includes a single first flow path groove, a plurality of second flow path grooves, and a branch portion that connects an end portion of the first flow path groove to end portions of the second flow path grooves. The branch portion includes a narrow portion having a narrower groove width than a groove width of a remaining portion of the branch portion. A groove depth of the narrow portion is shallower than a groove depth of the remaining portion of the branch portion.