Abstract: The present invention relates to a metallic nanoparticle catalyst, and more particularly, to a porous catalyst in which metallic nanoparticles are embedded in a porous oxide support, and a method for preparing the porous catalyst. To this end, a porous catalyst composition having metallic nanoparticles of the present invention includes an oxide matrix structure having mesopores and micropores; and metal or metal oxide nanoparticles embedded in the oxide matrix structure having the mesopores and micropores. Thus, metallic nanoparticle catalysts having high activity even at low temperature are realized.