A ceramic honeycomb structure including large numbers of flow paths partitioned by porous cell walls; (a) the cell walls having porosity of 55-65%; and (b) in a pore diameter distribution in the cell walls measured by mercury porosimetry, (i) a pore diameter at a cumulative pore volume corresponding to specific percentages of the total pore volume being within specific ranges and satisfying specific relationships; (ii) the difference of a logarithm of the pore diameter at a cumulative pore volume corresponding to 20% of the total pore volume and a logarithm of the pore diameter at 80% being 0.39 or less; and (iii) the volume of pores of more than 100 μm being 0.05 cm3/g or less.