To provide a rubber composition for breaker having balanced properties among rigidity, heat resistance, adhesiveness, humid aging adhesion and elongation, and a pneumatic tire having a breaker layer or a belt layer comprising the rubber composition. A rubber composition for breaker comprises 55 to 65 parts by weight of carbon black, 5 to 15 parts by weight of silica, 3.5 to 4.5 parts by weight of sulfur, at least 0.08 part by weight of cobalt, a resorcinol resin and a methylene donor based on 100 parts by weight of a rubber component containing a natural rubber and/or an isoprene rubber as a main component.