A nonwoven fabric for a filter excellent in cleaning efficiency and trapped matter retention volume is constructed by two or more different kinds of fibrous layers placed one over the other. The nonwoven fabric has an average pore size from 30 m inclusive to 60 m inclusive and a total pore area at 0.011 cm²/cm² or more with respect to an entire surface of the nonwoven fabric. The average pore size is calculated according to a bubble point method as defined in ASTM F-316-80 with use of a Coulter Porometer II.