The present invention provides a high pressure tank. The high pressure tank (10) includes: a resin liner (14) for containing a fluid; a reinforced layer (12) covering an outer surface of the liner (14); and a cap (16) including a supply/discharge hole (32) for supplying and discharging the fluid to and from the liner (14). Gas vent passages (64) formed in the cap (16) each including at one end a first opening open (60) toward the cap-facing surface (26) of the liner (14) and at the other end of a second opening open (62) toward at least one of an inside of the supply/discharge hole and an outside of the reinforced layer (12). A cross-sectional area of the gas vent passage (64) at the one end perpendicular to a longitudinal direction and the first opening (60) are smaller than other cross-sectional areas of the gas vent passage(64) perpendicular to the longitudinal direction.