A panel joint structure including: a first panel; a second panel that forms a space between itself and the first panel; a joint portion; a seal member that seals a gap between a distal end portion of the joint flange portion and the second panel; and a first panel bead portion that is formed in a region of the joint flange portion adjacent to the joint portion in the lengthwise direction of the first panel, that projects in a direction away from the second panel, that extends from a distal end to a base end of the joint flange portion, that forms with the second panel an air vent hole communicated with the space, and that slopes in a direction away from the second panel heading toward the base end side of the joint flange portion as seen from the lengthwise direction of the first panel.