Target substance-capturing device and target substance detection device

Provided is a target substance-capturing device (10) that comprises: a support member that supports a metal film-coated structure that captures a target substance and that is mounted on the support member, and that comprises at least two holes that open at a part of the support member other than the part on which the metal film-coated structure is mounted; a holding member that is used with the support member to sandwich the metal film-coated structure therebetween and that comprises an opening at which the holes of the support member overlap with the target substance-capturing part of the metal film-coated structure that is mounted on the support member; and a covering member that is translucent and that covers the opening of the holding member.