A multicore fiber includes: a center core that propagates four LP mode light beams including an LP02 mode light beam; and a first to a fifth cores disposed on a first line to a fifth line segments extend from the center of the center core in the radial direction at predetermined angles. The multicore fiber includes a different mode interaction section in which the propagation constants of each mode light beam propagated through the center core are matched with the propagation constants of LP01 mode light beams propagated through the first to fifth cores.