An exterior panel for a vehicle having a structure for preventing water from remaining therein, may include reinforcing ribs having a shape inclined downward, integrally formed on an inner surface of the panel, and disposed in a staggered arrangement at left and right sides of the panel, such that zigzag-shaped water drain routes, which guide water flowing into the panel in a downward direction, are formed on the inner surface of the panel, wherein lower end portions of the reinforcing ribs are adjacent to each other in upward and downward directions.