To provide a solar panel installation structure which can very easily adjust a position of a bolt to an appropriate position.

A solar panel installation structure includes: a plurality of fixtures which are installed on a sheathing roof board and fixed to a plurality of rafters, respectively, by screws penetrating the sheathing roof board and driven into the rafters; an installation rail which is stretched between and fixed to the plurality of fixtures; a bolt whose head is slidably fixed to the installation rail and whose screw part projects upward to be inserted through a through hole formed in a roof material fixed on the sheathing roof board; and a panel support part which is fixed on the roof material by the bolt to hold a solar panel.