The present application discloses a developing device including a housing having a connection surface to which the container connects. The connection surface is provided with a feed port for feeding the developer. The developing device includes a shutter mechanism configured to selectively open and close the feed port. The shutter mechanism includes a shutter piece, which moves between a closing position for closing the feed port and an opening position for opening the feed port, and a squeezing mechanism, which protrudes from the shutter piece situated in the closing position to squeeze the developer into the housing through the feed port.