To provide a honeycomb heat-storage unit for regenerative combustion equipment utilizing waste casting sand exhausted from a casting factory, and to provide a method for producing the honeycomb heat-storage unit.

Waste casting sand collected in a casting factory is temporarily fired at 500 to 900°C. The temporarily fired waste casting sand is admixed with an organic binder and a dispersion medium to prepare a raw material composition. A molded body with a honeycomb shape is molded from the raw material composition by extrusion molding. The molded body subjected to the extrusion molding is dried, and the molded body is subjected to normal firing at 1,000 to 1,300°C. Thus, the honeycomb heat-storage unit for the regenerative combustion equipment is obtained. The honeycomb heat-storage unit has the three phases of quartz, cristobalite and cordierite as the main crystal phases.