A honeycomb structure having porous partition walls having a large number of pores, formed so as to produce a plurality of cells each extending between the two ends of the honeycomb structure, and plugged portions formed so as to plug the cells at either one end of the honeycomb structure or at the insides of the cells, wherein the honeycomb structure has the partition walls of a permeability of 7×10−12 to 4×10−8 m2. The honeycomb structure can provide a honeycomb catalyst structure which is superior in purification efficiency, is low in pressure loss and can be mounted even in a limited space.