An automatic analysis device for analyzing a sample based on light detected by a detector, the automatic analysis device comprising: a reaction container; a reaction disk configured to hold the reaction container; a sample dispensing mechanism configured to dispense the sample to the reaction container; a reagent dispensing mechanism configured to dispense a reagent to the reaction container; an optical system including a light source which applies light to a mixture of the sample and the reagent dispensed to the reaction container, and the detector which detects the light applied from the light source; wherein the reaction container includes a photometric range in which light applied to the reaction container from the light source passes through the reaction container toward the detector; and a cleaning mechanism configured to clean the reaction container, wherein the cleaning mechanism includes a cleaning liquid supply nozzle which supplies a cleaning liquid to the reaction container after an analysis, a cleaning liquid suction nozzle which suctions the supplied cleaning liquid, and a cleaning tip provided on a lower end of the cleaning liquid suction nozzle, characterized in that the cleaning tip is configured such that, in a state where the cleaning tip is inserted into the reaction container, and at least a side surface of the cleaning tip opposes the light source and a side surface of the cleaning tip opposes the detector, a first region of the side surface, larger than the photometric range in the height direction, is formed such that the width becomes smaller downward, asecond region of the side surface which does not overlap the photometric range in the height direction, is positioned above the first region and has the same width as an upper end part of the first region, and a volume of a clearance between an inner wall of the reaction container and the cleaning tip is less than or equal to a volume of an inner hole, which is a liquid flow path when the cleaning liquid is suctioned by the cleaning liquid suction nozzle. a reaction container; a reaction disk configured to hold the reaction container; a sample dispensing mechanism configured to dispense the sample to the reaction container; a reagent dispensing mechanism configured to dispense a reagent to the reaction container; an optical system including a light source which applies light to a mixture of the sample and the reagent dispensed to the reaction container, and the detector which detects the light applied from the light source; wherein the reaction container includes a photometric range in which light applied to the reaction container from the light source passes through the reaction container toward the detector; and a cleaning mechanism configured to clean the reaction container, wherein the cleaning mechanism includes a cleaning liquid supply nozzle which supplies a cleaning liquid to the reaction container after an analysis, a cleaning liquid suction nozzle which suctions the supplied cleaning liquid, and a cleaning tip provided on a lower end of the cleaning liquid suction nozzle, characterized in that the cleaning tip is configured such that, in a state where the cleaning tip is inserted into the reaction container, and at least a side surface of the cleaning tip opposes the light source and a side surface of the cleaning tip opposes the detector, a first region of the side surface, larger than the photometric range in the height direction, is formed such that the width becomes smaller downward, asecond region of the side surface which does not overlap the photometric range in the height direction, is positioned above the first region and has the same width as an upper end part of the first region, and a first region of the side surface, larger than the photometric range in the height direction, is formed such that the width becomes smaller downward, asecond region of the side surface which does not overlap the photometric range in the height direction, is positioned above the first region and has the same width as an upper end part of the first region, and a volume of a clearance between an inner wall of the reaction container and the cleaning tip is less than or equal to a volume of an inner hole, which is a liquid flow path when the cleaning liquid is suctioned by the cleaning liquid suction nozzle.