An electrophotographic image forming apparatus, comprising: an apparatus body; a drive coupling disposed in the apparatus body of the image forming apparatus; a drive unit to rotate the drive coupling; a controller to control the drive unit; a developer unit detachably attachable to the apparatus body of the image forming apparatus; a driven coupling connected to the developer unit; and a toner supply unit to supply toner or developer to the developer unit in an image forming process, wherein: when the developer unit is attached to the apparatus body of the image forming apparatus, the driven coupling is configured to engage the drive coupling and the developer unit is driven by the drive unit; characterised in that: the image forming apparatus includes a toner ejection mode to discharge residual toner contained inside the toner supply unit when the developer unit is replaced with another developer unit having a different type of toner; the controller is configured to control the drive unit to cause the drive coupling to stop at a predetermined rotation stop position in the toner ejection mode; and in a mode other than the toner ejection mode, the controller is configured to control the drive unit to cause the drive coupling to stop at an arbitrary rotation stop position immediately when the drive coupling is rotating. an apparatus body; a drive coupling disposed in the apparatus body of the image forming apparatus; a drive unit to rotate the drive coupling; a controller to control the drive unit; a developer unit detachably attachable to the apparatus body of the image forming apparatus; a driven coupling connected to the developer unit; and a toner supply unit to supply toner or developer to the developer unit in an image forming process, wherein: when the developer unit is attached to the apparatus body of the image forming apparatus, the driven coupling is configured to engage the drive coupling and the developer unit is driven by the drive unit; characterised in that: the image forming apparatus includes a toner ejection mode to discharge residual toner contained inside the toner supply unit when the developer unit is replaced with another developer unit having a different type of toner; the controller is configured to control the drive unit to cause the drive coupling to stop at a predetermined rotation stop position in the toner ejection mode; and in a mode other than the toner ejection mode, the controller is configured to control the drive unit to cause the drive coupling to stop at an arbitrary rotation stop position immediately when the drive coupling is rotating. when the developer unit is attached to the apparatus body of the image forming apparatus, the driven coupling is configured to engage the drive coupling and the developer unit is driven by the drive unit; characterised in that: the image forming apparatus includes a toner ejection mode to discharge residual toner contained inside the toner supply unit when the developer unit is replaced with another developer unit having a different type of toner; the controller is configured to control the drive unit to cause the drive coupling to stop at a predetermined rotation stop position in the toner ejection mode; and in a mode other than the toner ejection mode, the controller is configured to control the drive unit to cause the drive coupling to stop at an arbitrary rotation stop position immediately when the drive coupling is rotating. the image forming apparatus includes a toner ejection mode to discharge residual toner contained inside the toner supply unit when the developer unit is replaced with another developer unit having a different type of toner; the controller is configured to control the drive unit to cause the drive coupling to stop at a predetermined rotation stop position in the toner ejection mode; and in a mode other than the toner ejection mode, the controller is configured to control the drive unit to cause the drive coupling to stop at an arbitrary rotation stop position immediately when the drive coupling is rotating.