A panel joint structure comprising: a first panel that is formed in an elongated shape and has a joint flange portion formed at one end portion or both end portions of the first panel as seen from a lengthwise direction; a second panel that is disposed opposing the joint flange portion in a thickness direction of the joint flange portion, that is joined to the joint flange portion, and that forms a space between itself and the first panel; a joint portion that defines the section of the joint flange portion joined to the second panel and that is formed along a lengthwise direction of the first panel; a seal member that seals a gap between a distal end portion of the joint flange portion and the second panel; and the panel joint structure being characterized in that it further comprises 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, and that forms with the second panel an air vent hole in communication with the space between the first panel and the second panel, wherein the first panel bead portion 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, and/or whose width dimension as seen from the thickness direction of the joint flange portion is set so as to be larger at the distal end of the joint flange portion than at the base end of the joint flange portion. a first panel that is formed in an elongated shape and has a joint flange portion formed at one end portion or both end portions of the first panel as seen from a lengthwise direction; a second panel that is disposed opposing the joint flange portion in a thickness direction of the joint flange portion, that is joined to the joint flange portion, and that forms a space between itself and the first panel; a joint portion that defines the section of the joint flange portion joined to the second panel and that is formed along a lengthwise direction of the first panel; a seal member that seals a gap between a distal end portion of the joint flange portion and the second panel; and the panel joint structure being characterized in that it further comprises 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, and that forms with the second panel an air vent hole in communication with the space between the first panel and the second panel, wherein the first panel bead portion 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, and/or whose width dimension as seen from the thickness direction of the joint flange portion is set so as to be larger at the distal end of the joint flange portion than at the base end of the joint flange portion.