A flush operating apparatus includes: a flush valve for opening and closing a discharge port on a storage tank; a manual operating unit, provided on the flush water tank and capable of manually operating the motion of the flush valve; a powered operating unit capable of operating the motion of the flush valve with power; and a control device for receiving a toilet flush start signal transmitted from either an instruction device by which a user instructs a toilet flush operation, or from a body sensor for sensing a user and activating a power drive motor; wherein the powered operating unit is separately installed from the manual operating unit, and is installed so as to be removable from the flush water tank in accordance with flush water tank apparatus or toilet main unit usage conditions.