A honeycomb filter includes an outer wall having a substantially cylindrical shape and a central axis of the substantially cylindrical shape, first walls provided at an inner side of the outer wall and extending along the central axis, and second walls provided at the inner side of the outer wall and extending along the central axis. The first walls and the second walls substantially perpendicularly cross to define cells having a substantially square shape in a cross-section perpendicular to the central axis. A thickness of the outer wall in the cross-section at a first intersection between the outer wall and a first diameter substantially parallel to the first walls in the cross-section and a thickness of the outer wall in the cross-section at a second intersection between the outer wall and a second diameter substantially parallel to the second walls in the cross-section are largest.