An automatic analyzer comprising: a reagent dispensing mechanism for dispensing reagent from reagent containers containing the reagent; information reading/writing means for recording and reading reagent information on and from an information recording medium provided on each reagent container; a reagent depository for storing a plurality of the reagent containers; a replenishment reagent depository for storing a reagent container; a reagent transfer mechanism for transferring the reagent container from the replenishment reagent depository to the reagent depository; and a reagent discharge mechanism comprising a storing portion for storing a reagent container discharged from the replenishment reagent depository; wherein at least one of the reagent depository, the replenishment reagent depository and the reagent transfer mechanism includes the information reading/writing means; wherein the automatic analyzer includes control means for exercising control such that the information reading/writing means writes the reagent information on the information recording medium immediately before the reagent container is transferred from the replenishment reagent depository to the reagent depository or immediately before the reagent container is discharged from the replenishment reagent depository to the storing portion; wherein the control means are adapted to measure elapsed time of the reagent container being placed in the replenishment reagent depository and to store the placing elapsed time; and wherein the information reading/writing means are adapted to write the placing elapsed time immediately before the reagent container is transferred from the replenishment reagent depository to the reagent depository. a reagent dispensing mechanism for dispensing reagent from reagent containers containing the reagent; information reading/writing means for recording and reading reagent information on and from an information recording medium provided on each reagent container; a reagent depository for storing a plurality of the reagent containers; a replenishment reagent depository for storing a reagent container; a reagent transfer mechanism for transferring the reagent container from the replenishment reagent depository to the reagent depository; and a reagent discharge mechanism comprising a storing portion for storing a reagent container discharged from the replenishment reagent depository; wherein at least one of the reagent depository, the replenishment reagent depository and the reagent transfer mechanism includes the information reading/writing means; wherein the automatic analyzer includes control means for exercising control such that the information reading/writing means writes the reagent information on the information recording medium immediately before the reagent container is transferred from the replenishment reagent depository to the reagent depository or immediately before the reagent container is discharged from the replenishment reagent depository to the storing portion; wherein the control means are adapted to measure elapsed time of the reagent container being placed in the replenishment reagent depository and to store the placing elapsed time; and wherein the information reading/writing means are adapted to write the placing elapsed time immediately before the reagent container is transferred from the replenishment reagent depository to the reagent depository.