A photonic bandgap fiber includes a hollow core formed along a center axis of the photonic bandgap fiber, through which a light propagates and a cladding region made of silica glass. The cladding region includes air holes forming a triangular lattice arranged around the hollow core. A lattice constant of the triangular lattice of the air holes Λ is equal to or smaller than 2.1 μm. Confinement loss in a predetermined wavelength range including a center wavelength of a photonic bandgap is lower than scattering loss.