To provide the locking mechanism of a safe door wherein the safe is opened without breaking the locking mechanism, even when one of four code locks gets trouble in the locking mechanism of the safe door, to which the code locks are installed.

In the locking mechanism 1 of the safe door operated when the safe door is opened and closed, a moving plate (a lateral moving plate 4) interlocked with an open-close handle 5 mounted on the surface side of the safe door and selectively moved at a locking place and an unlocking place on the rear side of the safe door, a locking piece 3 rotatably fixed on the rear side of the safe door at the same place, where the locking piece 3 is abutted or separated against or from a latch 4a secured to the moving plate (the lateral moving plate 4) on the rear side of the safe door, and a movement transmission mechanism 2 adjusting the degree wherein the locking piece 3 and the latch 4a are abutted on the basis of the movements of the movable end sections 1A1 to 1D1 of the four code locks 1A to 1D fitted to the safe door are installed.