A folding box made of synthetic resin which a worker can surely grip and stably carry without a slip by gripping whichever edge parts of a hexahedron of a box with both hands is provided. The folding box includes a rectangular-tube shaped side wall configuration member 3 comprised of four side panels 1 made of hard synthetic resin, adjacent side ends of the four side panels 1 being foldably connected to each other through side panel connecting hinge parts 2, a bottom plate configuration member 6 comprised of connecting bottom pieces 4 made of hard synthetic resin which are foldably connected to bottom ends of the plurality of side panels 1 through bottom piece connecting hinge parts 5, and a lid configuration member 7 comprised of lid pieces 15 made of hard synthetic resin which are foldably connected to upper ends of the plurality of side panels 1 through lid piece connecting hinge parts 10. Nonslip parts 13 made of soft synthetic resin exposed to the outside are provided near edges of one or both surfaces adjacent to each other at right angle through edges of a hexahedron. The Nonslip parts are provided near all the sides of the hexahedron.