Abstract: There is disclosed an automatic biochemical analyzer having a sample turntable and a reaction turntable. Plural sample containers for holding samples are arrayed on the sample turntable. Plural reaction containers are arrayed on the reaction turntable. A sampling pipette draws in a sample from some sampling container and injects the sample into some reaction container. A reagent pipette draws in some reagent from some reagent container and injects the reagent into the same reaction container. The resulting mixture is stirred by a stirring device. Produced reaction products are detected by a detector. Let N be the number of the reaction containers on the reaction turntable. The reaction turntable is rotated in M pitches in one step. Note that M and N do not have any common factor. First and second injecting positions adjacent to each other are established as positions where the reagent pipette can inject a reagent into the reaction container in position.