The present invention provides a deck plate with which it is possible to easily take fire protection measures, and a mounting member capable of constituting the deck plate with which it is possible to easily take fire protection measures.　A deck plate (1) includes: a flat plate part (10) extending in a first direction (X) and a second direction (Y); and a rib part (20) in which ribs (21, 22) protruding from the flat plate part (10) toward one side (a) in a third direction (Z) and extending in the first direction (X) are arranged at intervals in the second direction (Y). The deck plate includes a suppression part (30) which, when said one side (a) is an upper side in the vertical direction, is fitted to another deck plate (1B) adjacent in the second direction (Y) to suppress the deck plate (1B) from falling toward a lower side in the vertical direction. A mounting member (431) is provided with: an engagement part (434) that can be engaged with a plate mating part of a rib (321); and a hook-like part (432) that is connected to the engagement part (434) and that extends to said one side (a). The hook-like part (432) is folded back to the opposite side from the engagement part (434) and to the other side (b) in the third direction (Z).