A photonic bandgap fiber comprising: a core region; and a cladding region having a plurality of high refractive index portions disposed in a triangular lattice shape to surround the core region, being a nineteen-cell core type, the high refractive index portions having a refractive index higher than a refractive index of the core region, the cladding region including a medium having a refractive index equal to the refractive index of the core region, the high refractive index portions being disposed within said medium of the cladding having a refractive index equal to the one of the core the photonic bandgap fiber being used in a state in which at least a part of the photonic bandgap fiber is bent at a predetermined radius, wherein the plurality of the high refractive index portions are disposed around the nineteen-cell core type in three layers, the first layer comprising 18 high refractive index portions disposed in a hexagonal shape and surrounding the core region, the second layer comprising 24 high refractive index portions disposed in a hexagonal shape surrounding said 18 high refractive index portions, and the third layer comprising 30 high refractive index portions disposed in a hexagonal shape surrounding said 24 high refractive index portions a V value is 1.5 or greater and 1.63 or less, and Expression and Expression below are satisfied where a relative refractive index difference of the high refractive index portion to the medium is defined as Δ%, a lattice constant is defined as A μm, and the predetermined bending radius is defined as R cm, A HOM + B HOM Λ + C HOM Λ 2 + D HOM Λ 3 ≦ Δ ≦ A FM + B FM Λ + C FM Λ 2 + D FM Λ 3 15 ≦ R ≦ 25 (where A HOM = 171.37687 + 2.093345 R − 0.1275714 R 2 B HOM = − 43.29906 + 0.530802 R + 0.011094 R 2 C HOM = 3.48397 − 0.098659 R + 0.000365 R 2 D HOM = − 0.09034 + 0.003584 R − 0.0000348 R 2 A FM = 89.98658 − 2.94759 R + 0.04246 R 2 B FM = − 17.33858 + 0.743907 R − 0.011185 R 2 C FM = 1.0904 − 0.054614 R + 0.0008568 R 2 and D FM = − 0.02229 + 0.001232 R − 0.00002 R 2). a core region; and a cladding region having a plurality of high refractive index portions disposed in a triangular lattice shape to surround the core region, being a nineteen-cell core type, the high refractive index portions having a refractive index higher than a refractive index of the core region, the cladding region including a medium having a refractive index equal to the refractive index of the core region, the high refractive index portions being disposed within said medium of the cladding having a refractive index equal to the one of the core the photonic bandgap fiber being used in a state in which at least a part of the photonic bandgap fiber is bent at a predetermined radius, wherein the plurality of the high refractive index portions are disposed around the nineteen-cell core type in three layers, the first layer comprising 18 high refractive index portions disposed in a hexagonal shape and surrounding the core region, the second layer comprising 24 high refractive index portions disposed in a hexagonal shape surrounding said 18 high refractive index portions, and the third layer comprising 30 high refractive index portions disposed in a hexagonal shape surrounding said 24 high refractive index portions a V value is 1.5 or greater and 1.63 or less, and Expression and Expression below are satisfied where a relative refractive index difference of the high refractive index portion to the medium is defined as Δ%, a lattice constant is defined as A μm, and the predetermined bending radius is defined as R cm, A HOM + B HOM Λ + C HOM Λ 2 + D HOM Λ 3 ≦ Δ ≦ A FM + B FM Λ + C FM Λ 2 + D FM Λ 3 15 ≦ R ≦ 25 (where A HOM = 171.37687 + 2.093345 R − 0.1275714 R 2 B HOM = − 43.29906 + 0.530802 R + 0.011094 R 2 C HOM = 3.48397 − 0.098659 R + 0.000365 R 2 D HOM = − 0.09034 + 0.003584 R − 0.0000348 R 2 A FM = 89.98658 − 2.94759 R + 0.04246 R 2 B FM = − 17.33858 + 0.743907 R − 0.011185 R 2 C FM = 1.0904 − 0.054614 R + 0.0008568 R 2 and D FM = − 0.02229 + 0.001232 R − 0.00002 R 2). A HOM = 171.37687 + 2.093345 R − 0.1275714 R 2 B HOM = − 43.29906 + 0.530802 R + 0.011094 R 2 C HOM = 3.48397 − 0.098659 R + 0.000365 R 2 D HOM = − 0.09034 + 0.003584 R − 0.0000348 R 2 A FM = 89.98658 − 2.94759 R + 0.04246 R 2 B FM = − 17.33858 + 0.743907 R − 0.011185 R 2 C FM = 1.0904 − 0.054614 R + 0.0008568 R 2 and D FM = − 0.02229 + 0.001232 R − 0.00002 R 2).