An analyzer that causes a sample and a reagent to react with each other and analyzes the sample, the analyzer including reagent containers that store reagents and include openings for putting in and taking out the reagents, inner lids that are provided to be movable relatively to the openings and used for opening and closing the openings, a container shelf that moves the reagent containers, and an opening/closing mechanism that opens and closes the openings by moving the inner lids using movement of the reagent containers.