A seal assembly has simple assembly structures, and provides secure sealing effects. A crawler-track connection structure allows the seal assembly to be easily mounted, and securely prevents overflow of a lubricant and the like to the outside. A pair of seal rings (1) and (1) individually having lip portions (23) and (23) are disposed such that each of the lip portions (23) and (23) protrudes in a direction opposing an axial direction, and a load seal ring (2) is compressed and inserted between the pair of seal rings (1) and (1). The load seal ring (2) exerts reaction forces on the pair of lip portions (23) and (23) outwardly in the axial direction.