A flush glass apparatus includes a fixed glass having an opening, an operation glass configured to open and close the opening of the fixed glass, a lower rail configured to slidably support a lower portion of the operation glass, a sealing member provided below the lower rail to seal a gap between an inner surface of the fixed glass and a vehicle body, one or more upper drain holes provided on the lower rail to discharge rainwater on the lower rail to a buffer area between the lower rail and the sealing member, and a drain induction member interposed between the inner surface of the fixed glass and the sealing member and providing a lower drain hole to discharge rainwater in the buffer area to the outside.