A method for removing leukocytes, whereby leukocytes can be removed at a higher level of performance in a short filtration time without clogging. A method comprising passing a leukocyte-containing liquid through a filter for removing leukocytes made of a nonwoven fabric having an average fiber diameter of from 0.3 to 3.0 .mu.m, and thus removing the leukocytes from the leukocyte-containing liquid, to give a leukocyte-free liquid, characterized by using a nonwoven fabric having a formation index (y) of 50 or less corresponding to a thickness of 0.3 mm; use of a leukocyte removal filter therefore; and the leukocyte removal filter.