To establish an upper structure of a sliding door of van type truck, whose sealing effect between a door, door frame, and upper beam is enhanced and appearance is improved.

The upper structure of a sliding door is structured from a body part 18 consisting of a hollow part having a rectangular section and a flange part 20 projected upward, and the upper beam 22 of a door frame is composed of an outer vertical plate 24 flush with the flange 20, the first inner horizontal plate 26 extending horizontally inward from the bottom of the vertical plate 24, inner vertical plate 28 extending downward from the edge of the first plate 26, and the second inner horizontal plate 30 extending horizontally inward from the bottom of the plate 28. To the undersurface of the plate 30 a guide rail 32 formed from an inverted groove-form member is fixed in a part near the inner surface of the flange 20, and a seal member 34 is attached to the inner surface of the flange 20 in the space bounded by the oversurface, vertical plate 28, and horizontal plate 26. A roller 36 sliding in the guide rail 32 is pivoted at one end of an arm member 38, whose other end is fixed to the upper surface of the door body.