Architectural bracket, building wall structure, and board material construction method

[Problem] To provide an architectural bracket that improves strength and that is suitable for achieving a high degree of freedom in the arrangement relationship with a fixed object in construction, and to provide a building wall structure and a board material construction method using the architectural bracket. [Solution] An architectural bracket X1 is provided with a first fixed section 10 including a surface 11 to be brought into contact with a structure, and a second fixed section 20 extending from the end of the first fixed section 10 on the opposite side from the surface 11 so as to intersect the first fixed section 10. The second fixed section 20 is provided with: a base material section 21 including a surface 21A; a rib 22; a first side wall 23; and a second side wall 24. The rib 22 protrudes from the base material section 21 and includes a surface 22A on the protruding end thereof. The first side wall 23 protrudes on the same side as the rib 22 from one end of the base material section 21 in the width direction W of the base material section 21. The second side wall 24 protrudes on the same side as the rib 22 from the other end of the base material section 21 in the width direction W.