A symplectic mapping is presented, describing the effect of the beam‐beam interaction in presence of synchrotron motion. In addition to the usual transverse kick, this mapping includes the longitudinal displacement of the collision point and the energy variation caused by the electric field of the opposite bunch. These two effects are shown to play a concurrent role in preserving symplecticity. The case of weak‐strong interaction ine+e−colliding rings is investigated by simulation, assuming only one betatron degree of freedom.