A hexagonal-cell honeycomb structure having a plurality of cell walls having a hexagonal shape in cross-section and forming a plurality of hexagonal cell passages, and a tubular skin layer surrounding the cell walls, The thickness of the basic cell walls is 140 μm or less and an inscribed circle diameter Da inscribed at an intersectional portion of the basic cell walls 2 and an cell pitch P having the relationship Da/P≧0.13.