A mixing device used in a fluidized catalytic cracking apparatus which mixes a feed and a catalyst, the device comprising: a cylindrical reaction container configured to continuously supply the catalyst by allowing the catalyst to fall in a vertical direction; a feed supply section configured to include a plurality of feed injection nozzles which are arranged along an outer circumference of the reaction container and through which the feed is supplied from an exterior of the reaction container to an interior of the reaction container; and a catalyst flow regulator (7; 17; 25) which is arranged in the reaction container and regulates a flow of the catalyst at an area to which the feed is injected from the feed injection nozzles, wherein the catalyst flow regulator (7; 17; 25) has no feed supply function, wherein a tip of a lower portion of the catalyst flow regulator (7; 17; 25) is arranged above an intersection point between an extended line of each of the feed injection nozzles and an axis of the reaction container, and wherein the mixing device is a downflow moving-bed reactor, in which the catalyst and the feed are allowed to flow in a direction which is the same as that of the gravity, characterized in that the feed injection nozzles point downstream to inject the feed in a downstream direction, the catalyst flow regulator (7; 17; 25) has a cylindrical structure or has a disk-shaped structure, which is bonded to an inner wall surface of the reaction container via a support portion or is a disk-shaped porous plate which is provided so that an outer circumference of the porous plate is fixed to an inner wall surface of the reaction container and has a plurality of through holes therein at a portion other than a central portion for forming a catalyst stream having a hollow tubular shape to be coaxial with the reaction container at an area to which the feed is injected from the feed injection nozzles, and the tip of the lower portion of the catalyst flow regulator (7; 17; 25) is arranged below a position shifted upward by a distance corresponding to D/4, wherein D is an inner diameter of the reaction container at a position of a tip of each of the feed injection nozzles, from a position of a tip of each of the feed injection nozzles in a vertical direction. a cylindrical reaction container configured to continuously supply the catalyst by allowing the catalyst to fall in a vertical direction; a feed supply section configured to include a plurality of feed injection nozzles which are arranged along an outer circumference of the reaction container and through which the feed is supplied from an exterior of the reaction container to an interior of the reaction container; and a catalyst flow regulator (7; 17; 25) which is arranged in the reaction container and regulates a flow of the catalyst at an area to which the feed is injected from the feed injection nozzles, wherein the catalyst flow regulator (7; 17; 25) has no feed supply function, wherein a tip of a lower portion of the catalyst flow regulator (7; 17; 25) is arranged above an intersection point between an extended line of each of the feed injection nozzles and an axis of the reaction container, and wherein the mixing device is a downflow moving-bed reactor, in which the catalyst and the feed are allowed to flow in a direction which is the same as that of the gravity, characterized in that the feed injection nozzles point downstream to inject the feed in a downstream direction, the catalyst flow regulator (7; 17; 25) has a cylindrical structure or has a disk-shaped structure, which is bonded to an inner wall surface of the reaction container via a support portion or is a disk-shaped porous plate which is provided so that an outer circumference of the porous plate is fixed to an inner wall surface of the reaction container and has a plurality of through holes therein at a portion other than a central portion for forming a catalyst stream having a hollow tubular shape to be coaxial with the reaction container at an area to which the feed is injected from the feed injection nozzles, and the tip of the lower portion of the catalyst flow regulator (7; 17; 25) is arranged below a position shifted upward by a distance corresponding to D/4, wherein D is an inner diameter of the reaction container at a position of a tip of each of the feed injection nozzles, from a position of a tip of each of the feed injection nozzles in a vertical direction.