  We propose a simple scheme for the spin filter by studying the coherent
transport of electrons through a double-bend structure in a quantum wire with a
weak lateral magnetic potential which is much weaker than the Fermi energy of
the leads. {\em Extremely large} spin polarized current in the order of {\em
micro-Ampere} can be obtained because of the strong resonant behavior from the
double bends. Further study suggests the roubustness of this spin filter.
