Provided are a reagent supply method and device capable of using up a reagent in a container without a remnant to the extent possible, and supplying the reagent to an analysis device without mixing air bubbles even when the remaining amount of the reagent is extremely small. The reagent supply device includes: at least one reagent container including: a container body for storing a liquid reagent and a reagent supply port arranged on the container body and a support member for supporting the at least one reagent container so that the reagent supply port is positioned on a lower side of the container body. The reagent supply port is sealed by a plug including at least one nozzle penetration portion. The at least one nozzle penetration portion is formed of a material having a Shore hardness of from A5° to A90°.
