Disclosed is a filter installed in a water-flowing path of a washing machine. The filter improves the washing effect and protects the water-flowing path in the washing machine. The filter can be easily assembled and disassembled outside the washing machine. The filter has a body being fixed to and penetrating through the housing of the washing machine, a mesh member inserted in the body to filter the washing liquid passing therethrough, a locking lid assembled integrally with and relatively rotatable to the mesh member, and an annular packing tightly wound on the mesh member to prevent leakage between the body and the mesh member. A user can insert the mesh member into the body, and then rotate the locking lid so that the first locking protuberances of the locking lid are engaged with the second locking protuberances, thereby the mesh member is assembled in the body.