The columnar honeycomb structure 10 extending along a central axis CL, including a first end surface 10a and a second end surface 10b, and a partition wall 10c forming a plurality of first flow passages Ra and a plurality of second flow passages Rb, in which the first flow passages Ra are opened at the side of the first end surface 10a and plugged at the side of the second end surface 10b, the second flow passages Rb are plugged at the side of the first end surface 10a and opened at the side of the second end surface 10b, and the honeycomb structure includes a circular row W formed by arranging the second flow passages Rb adjoining and partitioned by the partition wall 10c in a circular pattern.