A remote-operated drain plug apparatus comprising: a drain port which, in use, is provided in a tub; a valve member disposed in the drain port and opening and closing the drain port when moved upward and downward; an operating portion which, in use, is disposed in a substantially vertical wall and opening and closing the valve member; a release wire including a tubular outer tube and an inner wire disposed in the outer tube movably in forward and backward directions, the release wire transferring operation performed on the operating portion to the valve member, wherein the drain port is opened and closed by moving the inner wire forward and backward in the axial direction of the outer tube, the operating portion includes: an action body connected to the inner wire, an operating portion body formed of a box-shaped member connected to the outer tube and provided with a side-surface opening, and a knob attached to the operating portion body or the action body in such a way that the knob protrudes through the opening, the knob being movable forward and backward in a front-rear direction of the apparatus or upward and downward, the opening in the operating portion body being located in the tub, when the apparatus is in use, overflow drainage in which drain in the tub is discharged toward sewage being carried out when the water level in the tub reaches or goes beyond a fixed level in the opening; the apparatus is configured so that movement of the knob in one of the forward and backward directions or one of the upward and downward directions to open the drain port causes at least part of the opening to be blocked by the knob or the action body, so as to prevent an interior of the opening for the overflow drainage from being fully exposed to a user who looks into the opening obliquely downward, wherein: the operating portion body accommodates the action body slidably upward and downward in the operating portion body; and the knob protruding through the opening lowers the action body when the knob is moved in one of the forward and backward directions or one of the upward and downward directions, whereas the knob protruding through the opening lifts the action body in the operating portion body when the knob is moved in the other one of the forward and backward directions or the other one of the upward and downward directions. a drain port which, in use, is provided in a tub; a valve member disposed in the drain port and opening and closing the drain port when moved upward and downward; an operating portion which, in use, is disposed in a substantially vertical wall and opening and closing the valve member; a release wire including a tubular outer tube and an inner wire disposed in the outer tube movably in forward and backward directions, the release wire transferring operation performed on the operating portion to the valve member, wherein the drain port is opened and closed by moving the inner wire forward and backward in the axial direction of the outer tube, the operating portion includes: an action body connected to the inner wire, an operating portion body formed of a box-shaped member connected to the outer tube and provided with a side-surface opening, and a knob attached to the operating portion body or the action body in such a way that the knob protrudes through the opening, an action body connected to the inner wire, an operating portion body formed of a box-shaped member connected to the outer tube and provided with a side-surface opening, and a knob attached to the operating portion body or the action body in such a way that the knob protrudes through the opening, the knob being movable forward and backward in a front-rear direction of the apparatus or upward and downward, the opening in the operating portion body being located in the tub, when the apparatus is in use, overflow drainage in which drain in the tub is discharged toward sewage being carried out when the water level in the tub reaches or goes beyond a fixed level in the opening; the apparatus is configured so that movement of the knob in one of the forward and backward directions or one of the upward and downward directions to open the drain port causes at least part of the opening to be blocked by the knob or the action body, so as to prevent an interior of the opening for the overflow drainage from being fully exposed to a user who looks into the opening obliquely downward, wherein: the operating portion body accommodates the action body slidably upward and downward in the operating portion body; and the knob protruding through the opening lowers the action body when the knob is moved in one of the forward and backward directions or one of the upward and downward directions, whereas the knob protruding through the opening lifts the action body in the operating portion body when the knob is moved in the other one of the forward and backward directions or the other one of the upward and downward directions. the operating portion body accommodates the action body slidably upward and downward in the operating portion body; and the knob protruding through the opening lowers the action body when the knob is moved in one of the forward and backward directions or one of the upward and downward directions, whereas the knob protruding through the opening lifts the action body in the operating portion body when the knob is moved in the other one of the forward and backward directions or the other one of the upward and downward directions.