To provide a roof panel mounting structure for mounting a roof panel well to a purlin by positioning and fixing the roof panel to the purlin by the same member to smoothly perform positioning work and fixing work.

The roof panel 1 paneled with a rafter 3 mounted to a sheathing roof board 2 is placed on the purlin 4 which is a horizontal member of form shape. A roof fixture 7 comprising a rafter fixing part 8 and a hook part 9 is disposed between the roof panel 1 and the purlin 4. The rafter fixing part 8 is fixed to the rafter 3 of the roof panel 1. The hook part 9 formed in U-shape opened downstream from the side view with an upper horizontal piece 9a, a vertical piece 9b and a lower horizontal piece 9c is hooked and locked to an upper face flange 6 of the purlin 4 from the upper side and upstream side. The lower horizontal piece 9c disposed below the flange 6 is provided with a fastener 10 such as a bolt. The flange 6 is clamped by the tip of the fastener 10 and the upper horizontal piece 9a placed on the upper face of the flange 6 of the purlin 4.