A blind nut including an internal threaded portion, a hollow tubular portion adjacent to the internal threaded portion, and a flange with hole, formed at the end on the opposite side to the internally threaded portion. The internal threaded portion is inserted into an attaching hole of the attached-to member, a part of the tubular portion is plastically deformed to expand in diameter, and the attached-to member is held between the deformed expanded diameter portion and the flange. The internal threaded portion includes a first straight portion adjacent to the tubular portion, a first tapered portion with an outside diameter gradually decreasing from the first straight portion, a second straight portion with an outside diameter smaller than the first straight portion, a second tapered portion with an outside diameter decreasing from the first straight portion, and a third straight portion with an outside diameter smaller than the second straight portion.