A rubber crawler having a metal core which comprises metal core extensions formed at predetermined intervals along the lengthwise direction of the metal core of the rubber crawler, thereby avoiding the phenomenon of wheel separation which occurs during crawler operation Wherein the metal core extensions are assembled on the mutually opposite surfaces of which are inclined at a predetermined angle, and the overlapped portion (center portion) surfaces of the metal core extensions are formed to have an angle of inclination to each other, thereby supporting the X axis, Y axis, and Z axis displacements.