A honeycomb filter comprising: a honeycomb fired body including porous cell partition walls defining a plurality of cells that serve as channels of exhaust gas, exhaust gas introduction cells each having an open end at an exhaust gas inlet side and a plugged end at an exhaust gas outlet side, exhaust gas emission cells each having an open end at the exhaust gas outlet side and a plugged end at the exhaust gas inlet side, and an outer wall on the periphery thereof, wherein the cross-sectional shape of each exhaust gas introduction cell in a plane perpendicular to the longitudinal direction thereof is entirely uniform from the end at the exhaust gas inlet side to the end at the exhaust gas outlet side excluding the plugged portion, the cross-sectional shape of each exhaust gas emission cell in a plane perpendicular to the longitudinal direction thereof is entirely uniform from the end at the exhaust gas inlet side to the end at the exhaust gas outlet side excluding the plugged portion, the exhaust gas emission cells, except for the cells adjacent to the outer wall, are each adjacently surrounded fully by the exhaust gas introduction cells across the porous cell partition walls, the cross-sectional area of each exhaust gas emission cell is larger than the cross-sectional area of each exhaust gas introduction cell, and provided that the hydraulic diameter is given by the following equation and the area based on the given hydraulic diameter is given by the following equation, the ratio of the area based on the hydraulic diameter of an exhaust gas introduction cell to the cross-sectional area of the exhaust gas introduction cell is 0.95 to 0.98, and the ratio of the area based on the hydraulic diameter of an exhaust gas emission cell to the cross-sectional area of the exhaust gas emission cell is 0.7 to 0.9: Hydraulic diameter = 4 × cross-sectional area of cell / Cross-sectional peripheral length of cell Area based on the hydraulic diameter = π × ( Hydraulic diameter / 2) 2 a honeycomb fired body including porous cell partition walls defining a plurality of cells that serve as channels of exhaust gas, exhaust gas introduction cells each having an open end at an exhaust gas inlet side and a plugged end at an exhaust gas outlet side, exhaust gas emission cells each having an open end at the exhaust gas outlet side and a plugged end at the exhaust gas inlet side, and an outer wall on the periphery thereof, wherein the cross-sectional shape of each exhaust gas introduction cell in a plane perpendicular to the longitudinal direction thereof is entirely uniform from the end at the exhaust gas inlet side to the end at the exhaust gas outlet side excluding the plugged portion, the cross-sectional shape of each exhaust gas emission cell in a plane perpendicular to the longitudinal direction thereof is entirely uniform from the end at the exhaust gas inlet side to the end at the exhaust gas outlet side excluding the plugged portion, the exhaust gas emission cells, except for the cells adjacent to the outer wall, are each adjacently surrounded fully by the exhaust gas introduction cells across the porous cell partition walls, the cross-sectional area of each exhaust gas emission cell is larger than the cross-sectional area of each exhaust gas introduction cell, and provided that the hydraulic diameter is given by the following equation and the area based on the given hydraulic diameter is given by the following equation, the ratio of the area based on the hydraulic diameter of an exhaust gas introduction cell to the cross-sectional area of the exhaust gas introduction cell is 0.95 to 0.98, and the ratio of the area based on the hydraulic diameter of an exhaust gas emission cell to the cross-sectional area of the exhaust gas emission cell is 0.7 to 0.9: Hydraulic diameter = 4 × cross-sectional area of cell / Cross-sectional peripheral length of cell Area based on the hydraulic diameter = π × ( Hydraulic diameter / 2) 2