The present invention relates to an optical fiber having a configuration which enables utilization of nonlinear phenomena in the near-infrared region. The optical fiber is directed to a holey fiber having a core region extending along a predetermined axis and a cladding region with plural holes arranged along the core region. The plural holes are arranged to constitute plural layers about the core region in the cross-section orthogonal to the predetermined axis. The three holes constituting the first layer (the innermost layer) closest to the core region correspond to three vertexes from among the six vertexes of a regular hexagon and are placed such that the arrangement of the three holes has three-fold rotational symmetry. The optical fiber enables utilization of nonlinear phenomena in the near-infrared region, by properly adjusting the hole diameter d and the pitch L between adjacent holes from among the holes constituting a single layer.