Plugged honeycomb structure

A plugged honeycomb structure comprising:

• a honeycomb structure body having porous partition walls defining a plurality of cells which extends from an inflow-side end face to an outflow-side end face and becomes a through channel for a fluid;
• inflow-side plugging portions disposed in open ends of predetermined inflow cells in the outflow-side end face;
• and
• outflow-side plugging portions disposed in open ends of residual outflow cells in the inflow-side end face,
• wherein in a cross section of the honeycomb structure body which is perpendicular to an extending direction of the cells, the inflow cells are disposed to surround the outflow cell, and the number of the inflow cells is larger than the number of the outflow cells,
• the cross section has a plurality of intersecting portions of the partition walls each defining the inflow cells which are adjacent to each other, and
• in 60% or more of a total number of the intersecting portions, a relation between a diameter D1 of a circle inscribed in the intersecting portion and a diameter D0 of a circle inscribed in the partition wall defining the inflow cell and the outflow cell which are adjacent to each other satisfies Equation (1) mentioned below:
• D1/(√2×D0)=1.20 to 1.80. Equation (1):