A valve device for a fuel tank includes: a housing in which an opening is formed in a partition wall, and a fuel vapor discharge port is provided; and a float valve. A ventilation chamber is provided with a tubular wall that is configured to communicate with the fuel vapor discharge port, and a notch is formed in a lower portion of a tip portion in an extending direction of the tubular wall. The partition wall includes a ceiling wall in which the opening is formed, and a peripheral wall extends downward from a peripheral edge of the ceiling wall. A part of the peripheral edge of the ceiling wall and a part of the peripheral wall are positioned inside the tubular wall through the notch when viewed in an axial direction of the tubular wall and a valve axial direction.