PURPOSE: To easily adjust the spacings between V-shaped filter elements arranged to correspond to the grain sizes of dust while these filter elements are provided with the characteristics of the inertia sepn. type filter by reversing the directions of the peak parts of the filter elements in odd rows and even rows and arranging the peak parts of the filter elements of the even rows in the positions deviated from the positions of the peak parts of odd rows.

CONSTITUTION: The respective filter elements 1A arranged in the odd rows N1, N3,..., Nn-1 and arranged in plural rows and the respective filter elements 1B arranged in the even rows N2, N4,...Nn are arranged by reversing the directions of the peak parts 1a, 1b thereof forward and backward. Further, the respective peak parts of the filter elements 1B of the even rows N2, N4,...Nn are arranged in the positions deviated from the respective peak parts 1a of the filter elements 1A of the odd rows N1, N3,..., Nn-1. Of course, the respective surface parts 1c, 1d of the filter elements 1A, 1B are arranged in the direction approximately orthogonal with the fluid flow direction F of dusty fluid paths 2. Thus, S-shaped narrow flow passages 3 are formed and the dusty fluid repeats collision.