The Mode I and Mode II fracture toughness between differently oriented plies in graphite/epoxy composites was characterized using DCB and ENF tests. GIc was almost the same for the 0/0, 30/−30, and 60/−60 interfaces. GIc for the 0/0 interface was approximately 30% higher than for the 30/−30 and 60/−60 interfaces when the crack initiation was characterized at the onset of nonlinear response. A remarkable increase of fracture toughness also appeared as the crack propagated. In addition, the rising rate of fracture toughness, dGR/da, increased as the fiber orientation at the crack front inclined away from the delamination direction. This was because angled plies at delaminated surfaces were apt to cause transverse cracking as the fiber orientation of the angled plies inclined away from the delamination direction. Consequently, the increase of fracture surface increased the fracture toughness.