To improve a beam end part structural body suitable for joining a beam and a side face of the other beam or a column mutually.

This beam end part structural body has the beam and H-shaped or T-shaped reinforcing hardware provided additionally in a lower flange end part and/or an upper flange end part of the beam. The beam and the reinforcing hardware are mutually joined and integrated to form a beam end part as a two-step or three-step H-shaped structure end part. An upper flange and a lower flange of the two-step or three-step H-shaped structure end part are joined with the side face of the other beam or the column.