Filtration device comprising: - a filtration body comprising an external container with an internal compartment and a cartridge element which can be inserted into said internal compartment in an extractable manner, the filtration body having an inlet opening, an outlet opening and a through-flow space which extends along a direction of extension between a top end and a bottom end and which is in communication with said inlet opening and with said outlet opening, the through-flow space extends along a direction of extension and has an inner surface which is curved around said direction of extension; - a mesh filter which comprises or is formed by a meshed cylinder able to divide said through-flow space into an inlet chamber and an outlet chamber which are situated respectively upstream and downstream of said mesh filter with respect to a liquid flow which crosses said through-flow space from said inlet opening to said outlet opening; - a magnetic member which extends from said top end into said through-flow space along said direction of extension A, coaxially with the mesh filter and with an inner side of said external container so as to be acted on by a liquid flow which, during use, crosses said through-flow space; characterized in that the inner surface of said filtration body comprises a deflection surface configured to deviate a liquid flow entering into the through-flow space through the inlet opening and is configured to impart to a liquid flow entering via said inlet opening into said through-flow passage a helical movement directed from said top end to said bottom end so as to impart a centrifugal stress to said liquid flow wherein the cartridge element comprises an outer wall which comprises: - a first part designed to be arranged against an inner side of the internal compartment; - a second part spaced from the inner side so as to define a through-flow compartment for a liquid flow; - a third part which joins the first part to said second part and that defines the deflection surface wherein the mesh filter comprises a cylindrical wall which has a large number of holes or which comprises a meshwork which is fixed to the cartridge element so as to delimit the outlet chamber, on the outside of the cylindrical wall. - a filtration body comprising an external container with an internal compartment and a cartridge element which can be inserted into said internal compartment in an extractable manner, the filtration body having an inlet opening, an outlet opening and a through-flow space which extends along a direction of extension between a top end and a bottom end and which is in communication with said inlet opening and with said outlet opening, the through-flow space extends along a direction of extension and has an inner surface which is curved around said direction of extension; - a mesh filter which comprises or is formed by a meshed cylinder able to divide said through-flow space into an inlet chamber and an outlet chamber which are situated respectively upstream and downstream of said mesh filter with respect to a liquid flow which crosses said through-flow space from said inlet opening to said outlet opening; - a magnetic member which extends from said top end into said through-flow space along said direction of extension A, coaxially with the mesh filter and with an inner side of said external container so as to be acted on by a liquid flow which, during use, crosses said through-flow space; characterized in that the inner surface of said filtration body comprises a deflection surface configured to deviate a liquid flow entering into the through-flow space through the inlet opening and is configured to impart to a liquid flow entering via said inlet opening into said through-flow passage a helical movement directed from said top end to said bottom end so as to impart a centrifugal stress to said liquid flow wherein the cartridge element comprises an outer wall which comprises: - a first part designed to be arranged against an inner side of the internal compartment; - a second part spaced from the inner side so as to define a through-flow compartment for a liquid flow; - a first part designed to be arranged against an inner side of the internal compartment; - a second part spaced from the inner side so as to define a through-flow compartment for a liquid flow; - a third part which joins the first part to said second part and that defines the deflection surface