Abstract: A column-shaped porous honeycomb structured body forms a plurality of first flow passages that are opened on one end face and closed on the other end face and a plurality of second flow passages that are closed on the one end face and opened on the other end face. The honeycomb structured body comprises: central partition walls where sectional areas of each first flow passage and each second flow passage are individually constant in an axial direction; and other-end-side inclined partition walls where the sectional area of each first flow passage is shrank and the sectional area of each second flow passage is expanded from the central partition walls to the other end face. An axial-directional length of the other-end-side inclined partition wall is 4 mm or more.