Abstract: A floor panel for a raised floor system is provided, where the floor panel includes a plate member with at least one longitudinal groove and a reinforcing member at least a portion of which is inserted into the longitudinal groove. The longitudinal groove is formed on the plate member of the floor panel for a raised floor system, and a stick type reinforcing member and/or a plate type reinforcing member is inserted into the longitudinal groove. Thereby, a thickness of the floor panel can be reduced and at the same time high stiffness and light weight of the floor panel can be achieved, and so a better walking feeling can be obtained and wider spacing of pedestals can be achieved. By coating the plate with a waterproof composition, it is possible to overcome drawbacks of a size and strength thereof being changed and deteriorated by being exposed to moisture.