The invention provides an automatic analyzer suitable for efficient reagent management. The analyzer allows continued use of existing reagent information storage media because reagent ID information that is no longer needed is overwritten so that it is unrecognizable to any analyzer. The invention relates to a method for automatically analyzing particular properties of an analyte by putting the analyte and a reagent into a vessel and measuring the reacted analyte-reagent mixture. The analyzer of the invention comprises: an information reader/writer for reading or writing regent information to/from storage media attached to reagent vessels; means for managing reagent information read from the storage media; means for processing reagents based on the managed information; and means for overwriting reagent information that has been judged unnecessary based on the managed information so that the unnecessary information is unrecognizable to any analyzer.