An interlocking mechanism of both-side lock recliner for an automotive seat which has an interlocking mechanism for simultaneously controlling the lock and the release of right and left engaging mechanisms mounted at both sides of the seat and including right and left manipulating levers, auxiliary levers provided symmetrically at both sides of the seat, and an interlocking rod including hook formed at both ends thereof for engaging between the auxiliary levers of both sides. Thus, the interlocking mechanism can exactly transmit the manipulating force of the handle in the engaging portion between the interlocking rod end and the member engaged with the interlocking rod end without enhancing the dimensional accuracy.