Provided is an interlocking chain unit that has reliable and strong interlocking and avoids buckling, breaking, and bending of a rigidified chain portion. In the interlocking chain unit (100), the interlocking operation of an outer tooth link plate (112BZ) and an outer tooth link plate (112AY) that are just about to complete the interlocking operation is completed in a manner that causes a first inter-pin distance (d1) and a second inter-pin distance (d2) become substantially equal to each other, and causes a third inter-pin distance (d3) to approach the second inter-pin distance (d2).