An extended triangular lattice type photonic bandgap fiber, includes a cladding and a capillary core, the cladding having a plurality of holes disposed within a silica glass portion in a longitudinal direction of the fiber and arranged in an extended triangular lattice shape, the capillary core having a plurality of holes arranged in a triangular lattice shape, wherein the cross-sectional area of the respective holes in the capillary core is smaller than that of the respective holes in the cladding.