[Problem] To provide a slab construction method enabling a concrete slab to be constructed at a low cost in a building having beams of H-shaped steel, and a deck plate to be recovered and reused; and to provide a deck plate support device used in the slab construction method. [Solution] The deck plate support device (1a) is provided with: a driving metal (2) having a substantially C-shaped side profile comprising a connecting part (2c) and two gripping parts (2a, 2b) connected to the connecting part (2c) and disposed so as to face each other, the driving metal (2) being formed so that the flange (5a) of the H-shaped steel (5) can be inserted between the gripping parts (2a, 2b); a block (3) attached to the driving metal (2) so that the end part (6a) of a deck plate (6) can be placed on the upper surface; and bolts (4a, 4b). Screw holes (4c, 4d), which threadedly engage with the bolts (4a, 4b), are formed in the gripping parts (2a, 2b) of the driving metal (2). A through-hole (4e) is formed in the block (3) so
