We　prove　time-asymptotic　stability　toward　the　planar　rarefaction　wave　for　the　three-dimensional　full,　compressible　Navier-Stokes　equations　with　the　heat-conductivities　in　an　infinite　long　flat　nozzle　domain　R　x　T-2.　Compared　with　one-dimensional　case,　the　proof　here　is　based　on　our　new　observations　on　the　cancellations　on　the　flux　terms　and　viscous　terms　due　to　the　underlying　wave　structures,　which　are　crucial　for　overcoming　the　difficulties　due　to　the　wave　propagation　in　the　transverse　directions　x(2)　and　x(3)　and　its　interactions　with　the　planar　rarefaction　wave　in　x(1)　direction.