An image forming apparatus includes an image carrier, a developing roller, a transfer section, a developer container, and a main unit. The image carrier has a surface for allowing an electrostatic latent image to be formed thereon, and carries a developed image. The developer container includes a container body having a side wall extending in a first direction, a container shutter, and a developer discharge port. The container shutter covers or exposes the developer discharge port. The main unit includes a housing and a guide mechanism. The developer container is mounted into the mounting section while being guided by the guide mechanism, and subsequently the container body of the developer container is rotated in a first rotational direction so that the developer discharge port communicates with the developer supply port and the side wall of the developer container is oblique to the vertical plane at an angle.