The present embodiment relates to an MCF in which the strength of mode coupling or power coupling between adjacent cores included in one coupled-core group is set to an appropriate level to reduce a DGD. The MCF includes at least one coupled-core group. A core interval Λ between adjacent cores included in the coupled-core group is set such that a mode coupling coefficient between the adjacent cores at a wavelength of 1550 nm satisfies 2.6×100 [m−1] to 1.6×102 [m−1] or a power coupling coefficient between the adjacent cores at the wavelength of 1550 nm satisfies 1.3×10−3 [m−1] to 8.1×100 [m−1].