A foldable highchair includes four support rods and a cloth seat. A hinge base and a slide base are sleeved on each of the four support rods. Two folding rods intersected with each other are arranged between the every adjacent two support rods, and the two folding rods are hinged at an intersection. One end of each of the two folding rods is hinged with the corresponding hinge base, and the other end of each of the two folding rods is hinged with the corresponding slide base. A double-locking mechanism configured to control the two folding rods to be fixed or folded is arranged on the two folding rods between the adjacent two support rods in one group. The cloth seat is connected to the four support rods, and a feeding tray is arranged between the tops of the front two support rods.