An exhaust purification unit comprising: a selective reduction catalyst provided in an exhaust system of an internal combustion engine and selectively reducing a nitrogen oxide in exhaust by using ammonia as a reducing agent; an exhaust pipe transmitting exhaust gas to the selective reduction catalyst; a urea water injection device arranged to face an exhaust upstream end of the exhaust pipe and injecting urea water into the exhaust pipe; a mixer chamber connecting an exhaust downstream end of a casing that accommodates therein a catalyst and the exhaust upstream end of the exhaust pipe, and forming a flow path along which the exhaust gas flows from the casing and turns back to the exhaust pipe, the chamber including a first chamber arranged at the exhaust downstream end of the casing and having a circular arc-shaped side surface and a second chamber extending from the side surface of the first chamber and having a circular arc-shaped side surface, wherein a width of a flow path is narrowed from the first chamber to the second chamber and one sidewall is curved and recessed; and a flow adjustment part provided in the second chamber of the mixer chamber, and a flow adjustment member provided in the flow adjustment part, the flow adjustment member being a pipe material having a truncated-cone shape which extends from a vicinity of an injection port of the urea water injection device towards the exhaust pipe with a diameter thereof gradually increasing from an upstream side towards a downstream side, in which a plurality of ventilation holes is formed, and in which a guide that guides the exhaust gas towards an exhaust downstream-side is provided for each of the plurality of ventilation holes, characterized by each guide being bent at an acute angle towards an inner side of the flow adjustment member at an upstream side of a corresponding one of the ventilation holes, wherein a large-diameter opening of the flow adjustment member is partially inserted in an exhaust upstream end of the exhaust pipe, and a gap through which the exhaust gas passes is provided between an outer peripheral surface of an edge portion of the large-diameter opening of the flow adjustment member and an inner peripheral surface of the exhaust upstream end of the exhaust pipe. a selective reduction catalyst provided in an exhaust system of an internal combustion engine and selectively reducing a nitrogen oxide in exhaust by using ammonia as a reducing agent; an exhaust pipe transmitting exhaust gas to the selective reduction catalyst; a urea water injection device arranged to face an exhaust upstream end of the exhaust pipe and injecting urea water into the exhaust pipe; a mixer chamber connecting an exhaust downstream end of a casing that accommodates therein a catalyst and the exhaust upstream end of the exhaust pipe, and forming a flow path along which the exhaust gas flows from the casing and turns back to the exhaust pipe, the chamber including a first chamber arranged at the exhaust downstream end of the casing and having a circular arc-shaped side surface and a second chamber extending from the side surface of the first chamber and having a circular arc-shaped side surface, wherein a width of a flow path is narrowed from the first chamber to the second chamber and one sidewall is curved and recessed; and a flow adjustment part provided in the second chamber of the mixer chamber, and a flow adjustment member provided in the flow adjustment part, the flow adjustment member being a pipe material having a truncated-cone shape which extends from a vicinity of an injection port of the urea water injection device towards the exhaust pipe with a diameter thereof gradually increasing from an upstream side towards a downstream side, in which a plurality of ventilation holes is formed, and in which a guide that guides the exhaust gas towards an exhaust downstream-side is provided for each of the plurality of ventilation holes, characterized by each guide being bent at an acute angle towards an inner side of the flow adjustment member at an upstream side of a corresponding one of the ventilation holes, wherein a large-diameter opening of the flow adjustment member is partially inserted in an exhaust upstream end of the exhaust pipe, and a gap through which the exhaust gas passes is provided between an outer peripheral surface of an edge portion of the large-diameter opening of the flow adjustment member and an inner peripheral surface of the exhaust upstream end of the exhaust pipe.