Flow switching device for catheterization with a three way catheter comprising: a housing having an internal cylindrical surface, in which four openings are obtained which are arranged the one after the other one, angularly separated by an angle between 80° and 90°, from three of which a conduct originates； a hydraulic bifurcation originating from the remaining fourth opening and which provides distally other two conducts； and switching means comprising: another cylindrical surface, which is outer, holed and introducible in the housing to close at least two openings； an internal greater hydraulic pipeline which connects a first couple of holes, obtained in the other surface and spaced of an angle between 170° and 190°, an internal smaller hydraulic pipeline which is internal； lateral and which connects another couple of holes obtained in the other cylindrical surface； wherein the openings and the holes are configured to allow two configurations in which the greater pipeline connects only two not consecutive openings and the smaller one does not connect any opening； and two configurations in which the smaller pipeline connects only two consecutive openings and the greater one does not connect any opening.
