PURPOSE: To enhance washing efficiency by a method wherein a cake is scraped off on the way of the running of a sheet like filter material while the filter material is allowed to run from one side to the other side and washing is performed in the order of brush washing and shower washing to regenerate the filter material.

CONSTITUTION: Washing is performed at least in the order of the scraping-off of a cake by a scraper 90, the brush washing due to a brush 98 and the washing due to a high pressure shower jet orifice 102 on the way of the running of a sheet like filter material 63 while the filter material 63 is allowed to run from one side to the other side to regenerate the filter material 63. As a result, the use amount of a washing solution can be suppressed and washing efficiency can be enhanced.