To provide a filter for exhaust gas which has high removing capability for harmful substances by a catalyst and low pressure loss.

This filter includes an outflow-side cell 81 and an inflow-side cell 82 arrayed alternately. The outflow-side cell 81 and inflow-side cell 82 each have a rectangular sectional shape such that all sides perpendicular to a direction in which gas (fluid) flows are surrounded with main partition walls 10. The outflow-side cell 81 is provided with sub partition walls 11, 12 projecting from two opposite main partition walls 10 respectively, and the sub partition walls 11, 12 are set not to be in contact with each other. Consequently, the space in the outflow-side cell 81 having the sub partition walls 11, 12 formed is not divided by the sub partition walls 11, 12.