An inflow indicator apparatus is for a well in an underground structure in which at least one tracer depot is arranged to be in contact with a partial fluid flow flowing from a producing structure into the well. The inflow indicator apparatus has a tubular body, a seal encircling a portion of the tubular body, arrangement of the at least one tracer depot externally on the tubular body, the seal being settable against an encircling wall, and the tubular body, the seal and the encircling wall defining an annulus forming a first flow path for the partial fluid flow which is separated from a second fluid flow path through the inflow indicator apparatus for a main fluid flow formed of a through fluid line in the tubular body, the first flow path extending from the seal to an end portion of the tubular body.