A developing device includes: a container configured to store a developer and have an agitating passage for supplying the developer to a developing roller; a rotatable agitating member configured to carry the developer along the agitating passage while agitating the developer; a discharge port configured to be provided a container wall surface on a side on which the developer is scraped down in the agitating passage and discharge an excess developer involved in the supply of the developer; and a heaping member configured to heap the developer near the discharge port and discharge the developer from the discharge port.