An air vent head having an air pipe with a downward opening is provided to remove a positive pressure state or a negative pressure state by communicating an inside of a tank of a ship with an outside atmosphere. An air vent head(100) having an air pipe(10) with a downward opening(11) includes a guide unit(300), a float(400), and an open unit(200). A plate(310) is fixed by a plurality of connection pieces(320) to guide in reduced speed by converting directions of air and fluid at a bottom of the opening of the air pipe. A guide rod(330) is installed on a bottom center of the plate. An insertion hole is prepared at a top of the float to insert the guide unit. A guide hole(420) is prepared at a bottom to insert the guide rod. A plurality of exit holes(230) are formed at a bottom of a cylindrical body(210). The open unit is fixed and installed by being separated at a predetermined distance from a ship body with a plurality of supporting pieces.
