An interbody cage includes a substrate having a plurality of curve slits, with each of the curve slits having a plurality of sections. A plurality of deformable ribs is formed, with each deformable rib between any adjacent two of the curve slits and having a first end and a second end. The first and second ends of each deformable rib respectively connect with two opposite lateral bars of the substrate, and a plurality of folds is formed on the plurality of deformable ribs in places adapted to be bent. In use, any adjacent two of the deformable ribs are capable of being bent to depart from each other to define a filling room.