PURPOSE: To provide a valve seat for high-powered internal combustion engine having superior wear resistance and reduced in attacks on a valve by specifying the dimension, shape, and distribution percentage of Al2O3 ceramic grains to be dispersed in the matrix of an iron-base sintered alloy, respectively.

CONSTITUTION: This valve seat has a structure where a shell-like hard phase having dimensions of 5-25μ average outside diameter and 1-10μ average thickness and composed principally of fine Al2O3 coagulated into shell-like state is distributed by 5-20vol.% into the matrix of an Fe-base sintered alloy. Because this valve seat is reduced in the falling of the Al2O3 grains from the matrix during use, attacks on a mating material are reduced and extremely superior wear resistance is provided. Further, even if the hard shell-like phase of <5μ average outside diameter and <1μ average thickness is distributed by <5vol.%, the improvement of wear resistance becomes insufficient. On the other hand, when the hard shell-like phase having >25μ average outside diameter and >10μ average thickness is distributed by >20vol%, the strength and toughness of the alloy cannot be improved and attacks on a mating material are increased, on the contrary.