The present invention relates to a core, a rotor, a motor and a compressor. It is an object of the present invention to prevent a short circuit of magnetic flux especially in a rotor. In order to attain this object, a rotor (1a) comprises a core (11) extending in a predetermined direction (91), and a plurality of magnets (21). The core (11) has parts (111, 112) formed by magnetic materials and extending in the predetermined direction (91). The parts (112) are arranged in a loop around the part (111), and face the part (111) through gaps (41). The magnets (21) are buried in the gaps (41) in the form of a loop in the core (11). The magnets (21) have pole faces (211, 212) extending in the predetermined direction (91). In each of the magnets (21), at least one of ends (21a, 21b) of the magnet (21) protrudes forward in the predetermined direction (91) with respect to an end (111a, 111b) of the part (111) that is on the same side with the at least one of the ends of the magnet.