We theoretically study the spin-dependent electron transport in a Rashba electron waveguide with rough edges,attached to ideal leads without spin-orbit interaction. The influence of the edge disorder on the charge and spin conductances is clarified by using the spin-resolved lattice Green function method.It is found that a spinpolarized current can be generated in the output lead and its spin polarization can be manipulated by varying the waveguide length.The underlying physics is attributed to the broken longitudinal symmetry and the spindependent quantum interference induced by the rough boundaries.Our results may provide a new method to design a spin filter without using magnetic materials or applying a magnetic field.