Concentration device and concentration method

A concentration device for concentrating a liquid containing a target object, the concentration device comprising:

• a container configured to store a liquid containing a target object;
• a filter in the container;
• a shaft configured to change a position of the filter in the container;
• one or more discharge flow paths extending through a side wall of the container;
• one or more supply flow paths extending through the side wall of the container and located lower than any of the one or more discharge flow paths;
• a supply tank connected to the one or more supply flow paths;
• and
• a first washing liquid flow path connected to the supply tank and configured to supply a washing liquid to the supply tank, wherein
• in a state where the liquid is stored in the container, a gas layer is present at a lower portion of the filter,
• the filter is sized such that there is a gap between an outer peripheral surface of the filter and an inner surface of the container that allows the filter to move within the container, and the gap has a size that prevents the target object from passing through the gap,
• through the one or more discharge flow paths, the liquid inside of the container is discharged to outside of the container, and
• through the one or more supply flow paths, the liquid containing the target object is supplied to the inside of the container.