Architectural bracket, building wall structure, and plank member construction method

Provided is an architectural bracket that has an improved strength, and is suitable for realizing a high degree of freedom in terms of the arrangement relationship with a fixation object in construction, as well as a building wall structure and a plank member construction method that use the architectural bracket. An architectural bracket X1 includes a first fixing portion 10 that includes a surface 11 for coming into contact with a building frame, and a second fixing portion 20 that extends from an end of the first fixing portion 10 to a side opposite to the surface 11, so as to intersects with the first fixing portion 10. The second fixing portion 20 includes a base portion 21 that includes a surface 21A, a rib portion 22, a first side-wall portion 23, and a second side-wall portion 24. The rib portion 22 protrudes from the base portion 21, and includes, at a protruding end thereof, a surface 22A. The first side-wall portion 23 protrudes from an end of the base portion 21 in the width direction W of the base portion 21 to the same side as the side to which the rib portion 22 protrudes. The second side-wall portion 24 protrudes from the other end of the base portion 21 in the width direction W to the same side as the side to which the rib portion 22 protrudes.