A developer supplier includes a developer container and a main unit. The main unit includes a mounting section for allowing the developer container to be mounted therein. The developer container includes a container body, a container shutter and a developer discharge port. The container shutter is supported on the container body and covers or exposes the developer discharge port. The main unit includes a housing and a guide mechanism. The housing is formed with a developer supply port. The developer container is mounted into a first position of the mounting section while being guided in a first direction by the guide mechanism, and subsequently the container body is rotated from the first position to a second position in a first rotational direction to thereby move and expose the developer discharge port away from the container shutter so that the developer discharge port communicates with the developer supply port.