A cooling device for a circuit breaker which comprises a case having a front wall, a rear wall, an upper wall, a lower wall, two flanks, and a first series of side-by-side terminals and a second series of side-by-side terminals that protrude outside from the case for the connection of the circuit breaker with an electrical circuit. The cooling device includes at least one first body made of a thermal conducting material and which has a central portion suitable for being positioned transversally along and facing the first series of terminals so as to absorb heat generated at the first series of terminals, and a first end portion and a second end portion that protrude from the central portion and are configured so as to receive the heat absorbed by the central portion and to diffuse it outside the cooling device itself.