To provides a filter which can reduce vibration of a filter element while maintaining high revolution speed.

There is provided a filter which comprises: a cylindrical main-body vessel 1; a tubular filter element 7 which is disposed in the main-body vessel 1 coaxially therewith and has a lot of filter pores 7a formed for removing foreign matter contained in liquid; an inflow pipe 5 which is disposed in a direction tangential to a circumferential wall surface of the main-body vessel 1, and which introduces liquid containing matter to be separated and generates a swirl flow in the liquid; an outflow pipe 8 for making filtrate obtained by filtration through the filter element 7 flow out; and a foreign matter discharge pipe 12 which is disposed in a direction tangential to the circumferential wall surface of the main-body vessel 1 and discharges the matter to be separated together with the liquid. In a surface which is a flow-in side of the filter element 7, ruggedness parts for forming a turbulence layer in the swirl flow are repeatedly formed.