To provide a filter device capable of shortening the time required in the replacement of a filter and capable of being operated efficiently.

In the filter device 1 constituted so that filters 8-10 for removing foreign matter in dampening water used in offset printing are provided in a replaceable manner and dampening water is allowed to flow out of an outflow pipeline 11 from inflow pipings 2-4 through the filters 8-10 in housings 5-7, a changeover valve 18 for supplying either one of dampening water and air for removing dampening water is provided to the inflow pipelines 2-4. Dampening water can be rapidly removed from the filters 8-10 without waiting the dropping of dampening water under its own weight to rapidly replace the filters 8-10.