Abstract: Provided is a capillary electrophoresis device including a holder preventing a septum from coming off when a capillary is pulled out, and also allowing containers to be taken out in any order. In the capillary electrophoresis device for separating and analyzing a sample such as a DNA and a protein by electrophoresis, the holder includes: a septum having a capillary hole through which a capillary penetrates; a container for storing a solution; and a container-accommodation unit for accommodating the container. A hole formed in the septum engages with an engagement portion formed on the container, and thereby the septum is held to cover the container.