A catalyst body includes a catalytic layer containing an alkali metal and/or an alkaline earth metal and a carrier carrying the catalytic layer, characterized in that the carrier has a porosity of 40% or below. According to this catalyst body, the invasion of the alkali metal and/or the alkaline earth metal contained in the catalytic layer into the inside of the carrier is inhibited and thus the carrier can sustain the strength and NOx absorptivity required as a carrier over a long period of time even upon exposure to a high temperature.