PURPOSE: To effectively wash a spent filter medium to effectively reuse it when fluid is fed to a lumpy material to be washed to wash it while the lumpy material is sucked and conveyed, by jetting the fluid with high pressure to make it impinge on the lumpy material.

CONSTITUTION: In a washer 10, a material to be washed, such as a spent filter medium (lumpy material) 12 is first sucked by a sucking means, such as a vacuum blower car 16 through a pipe 14. Next, after the sucked filter medium 12 is classified by specific size by a classifying means, such as an automatic hopper 18, it is washed by a washing means 20. At this time, to the washing means 20 is connected a jetting means, such as a high pressure jet means 28. And fluid, such as water is jetted with high pressure from a high pressure jet means 28 to wash the filter medium 12. In this way, the spent filter medium 12 is effectively washed to make it reusable effectively.