To provide a fixture for a seam, capable of enhancing stability of a state of attachment to a seam portion.

A fixture for a seam, which is attached to a seam part X of a protrusive streak provided on a roof, includes first and second sandwiching bodies 1 and 2 for holding the seam part X in the state of sandwiching it. Each of the sandwiching bodies 1 and 2 comprises sandwiching parts 14 and 22 that are disposed along a direction orthogonal to a sandwiching direction. The first sandwiching body 1 comprises a screw hole 131 that is screwed to a screw body 3 so as to move the screw body 3 in the sandwiching direction, and a guide part 15 for guiding the second sandwiching body 2, which is moved by being pushed in the sandwiching direction by a leading end 31 of the screw body 3, along the sandwiching direction.