Provided is a multi-core fiber 1 for performing communication using light up to an xth-order LP mode (where x is an integer of 1 or more) in a communication band. The multi-core fiber 1 includes a plurality of signal light propagation cores 11 that propagate light up to an (x + 1)th-order LP mode and at least one high-loss core 15 that has a higher loss of propagated light than the signal light propagation cores 11. Crosstalk occurs between light of the (x + 1)th-order LP mode propagated through at least one signal light propagation core 11 and light of a primary LP mode propagated through at least one high-loss core 15.