A developer container is described that is capable of preventing the developer held inside the container from being squirted to the outside. A cartridge, an image formation unit and an image formation apparatus are described that are each provided with the developer container. The developer container has: a first member; a second member that is combined with the first member such that the first and second members form a developer storage room; and a third member that covers a boundary portion between the first member and the second member. An aspect of the invention is that it can prevent the developer from being squirted to the outside of the developer container.