A honeycomb catalyst body includes: porous partition walls having a large number of pores and disposed to form a plurality of cells communicating between two end faces, plugged portions disposed to plug each of the cells on one of the end faces, and catalyst layers loaded in layers on an inner surface of the cells and an inner surface of the pores and containing a noble metal. Mass (Mc) of the noble metal contained in the catalyst layer loaded on the inner surface of the cells and mass (Mp) of the noble metal contained in the catalyst layer loaded on the inner surface of the pores satisfy the relation of (Mp)/(Mc)≧4. The honeycomb catalyst body is excellent in purification efficiency, has low pressure loss, and is mountable even in a limited space.