A multi-stage mixer for placing inside a vehicle exhaust pipe found in an exhaust system for mixing the exhaust and urea flow in three stages so as to convert the same into a non-uniform flow structure that proceeds in both swirling and unsteady manner with swirl or reverse swirl flow characteristic and cross-flow characteristic; and comprising - at least one swirl generator comprising swirl plates configured to mix the exhaust gas and urea flow in the first stage and positioned with regard to each other such that they would form a circular structure, and ensuring, by means of the swirl plates and its circular hollow structure, conversion of the exhaust gas and urea flow into a flow characteristic in the form of a swirl or reverse swirl flow characteristic and allowing extension of the flow path via rotation, - at least one flow centralizer configured to perform the second mixing stage, and during the second mixing stage, configured to channel the flow incoming with swirl or reverse swirl flow characteristic towards the central part of the pipe by centering the flow by means of the channelers found thereon, - the flow centralizer found in the flow direction of the exhaust gas, after the swirl generator, configured to center the flow leaving the swirl generator with a swirl or reverse swirl flow characteristic, and comprising at least one outer frame, at least one cross-flow generator fixed in the flow centralizer in a concentric manner with the flow centralizer, configured to perform the third mixing stage, comprising middle vanes, side vanes, and a connecting plate, and configured to channel the flow with swirl or reverse swirl flow characteristic hitting onto the middle vanes and side vanes, found at different distances and positions with regard to each other on the connecting plate, towards opposite directions to each other and thus converting the flow into a flow with a cross-flow characteristic, characterized in that the flow centralizer comprises a channeler, a gap, and at least one channel, - gaps found at the front part of the outer frame, at the section where the exhaust gas and urea exit, at the channelers which start from the edge part of the outer frame and extend towards the center of the outer frame and at both sides of the channelers, and which have a narrower structure at the edge of the outer frame and a broader structure at the channeler tips which are closer to the center. - at least one swirl generator comprising swirl plates configured to mix the exhaust gas and urea flow in the first stage and positioned with regard to each other such that they would form a circular structure, and ensuring, by means of the swirl plates and its circular hollow structure, conversion of the exhaust gas and urea flow into a flow characteristic in the form of a swirl or reverse swirl flow characteristic and allowing extension of the flow path via rotation, - at least one flow centralizer configured to perform the second mixing stage, and during the second mixing stage, configured to channel the flow incoming with swirl or reverse swirl flow characteristic towards the central part of the pipe by centering the flow by means of the channelers found thereon, - the flow centralizer found in the flow direction of the exhaust gas, after the swirl generator, configured to center the flow leaving the swirl generator with a swirl or reverse swirl flow characteristic, and comprising at least one outer frame, at least one cross-flow generator fixed in the flow centralizer in a concentric manner with the flow centralizer, configured to perform the third mixing stage, comprising middle vanes, side vanes, and a connecting plate, and configured to channel the flow with swirl or reverse swirl flow characteristic hitting onto the middle vanes and side vanes, found at different distances and positions with regard to each other on the connecting plate, towards opposite directions to each other and thus converting the flow into a flow with a cross-flow characteristic, characterized in that the flow centralizer comprises a channeler, a gap, and at least one channel, - gaps found at the front part of the outer frame, at the section where the exhaust gas and urea exit, at the channelers which start from the edge part of the outer frame and extend towards the center of the outer frame and at both sides of the channelers, and which have a narrower structure at the edge of the outer frame and a broader structure at the channeler tips which are closer to the center.