A developer supply apparatus includes a holding member for detachably holding a developer supply container having a developer discharge opening and a sealing member for sealing the developer discharge opening; a rotatable member rotatably supported on the holding member; a converting mechanism, provided at a connecting portion between the rotatable member and the holding member, for converting a rotation of the rotatable member to a sliding operation of the holding member; wherein the sealing member moves from a closing position to an opening position by the sliding operation.