A sample analyzer comprising: a reagent container set section (60a-60e) for setting a reagent container (200, 300) which contains a specific reagent, wherein a recording medium (260, 360) storing a kind information indicating a kind of the reagent is attached to the reagent container (200, 300); a reader/writer (61a-61e) configured to read out an information from the recording medium (260, 360) attached to the reagent container (200, 300) set in the reagent container set section (60a-60e) and configured to write an information on the recording medium (260, 360); an openable and closable cover which is provided in the reagent container set section (60a-60e); the sample analyzer being characterized by further comprising: a writing instruction section including a sensor configured to detect a closing of the cover, the writing instruction section being configured to issue an instruction to write the information on the recording medium (260, 360) if the sensor has detected the closing of the cover; a controller configured to control the reader/writer to write the information on the recording medium (260, 360) attached to the reagent container (200, 300) set in the reagent container set section (60a-60e) if the kind information read out from the recording medium (260, 360) indicates the specific reagent and the writing instruction section has issued the writing instruction. a reagent container set section (60a-60e) for setting a reagent container (200, 300) which contains a specific reagent, wherein a recording medium (260, 360) storing a kind information indicating a kind of the reagent is attached to the reagent container (200, 300); a reader/writer (61a-61e) configured to read out an information from the recording medium (260, 360) attached to the reagent container (200, 300) set in the reagent container set section (60a-60e) and configured to write an information on the recording medium (260, 360); an openable and closable cover which is provided in the reagent container set section (60a-60e); the sample analyzer being characterized by further comprising: a writing instruction section including a sensor configured to detect a closing of the cover, the writing instruction section being configured to issue an instruction to write the information on the recording medium (260, 360) if the sensor has detected the closing of the cover; a controller configured to control the reader/writer to write the information on the recording medium (260, 360) attached to the reagent container (200, 300) set in the reagent container set section (60a-60e) if the kind information read out from the recording medium (260, 360) indicates the specific reagent and the writing instruction section has issued the writing instruction. a writing instruction section including a sensor configured to detect a closing of the cover, the writing instruction section being configured to issue an instruction to write the information on the recording medium (260, 360) if the sensor has detected the closing of the cover; a controller configured to control the reader/writer to write the information on the recording medium (260, 360) attached to the reagent container (200, 300) set in the reagent container set section (60a-60e) if the kind information read out from the recording medium (260, 360) indicates the specific reagent and the writing instruction section has issued the writing instruction.