A sunroof unit for at least partially opening and closing an opening formed in a roof of a vehicle, the sunroof unit comprising: a frame configured to be disposed below the roof so as to be aligned with the opening; a rear panel secured to the frame to close a rear portion of the opening; and a front panel that includes a stay depending from a side portion thereof and is supported by the frame via the stay so as to be slidable between a closed position to close a front portion of the opening and an open position where the front panel overlaps on top of the rear panel to open the front portion of the opening, wherein the rear panel includes a rear panel main body and a rear molded part provided on an outer peripheral edge of the rear panel main body and contacts an edge of the opening via a rear seal portion, the rear seal portion includes a first seal member mounted to the rear molded part in a rear portion of the opening and a second seal member extending in a fore and aft direction and supported by the frame via a support bracket to form a passage for the stay between the second seal member and the rear molded part in a side portion of the opening, characterised in that the frame includes a pair of guide walls (41A, 41B) disposed more inboard than a side edge of the opening and slidably guiding a slider, which supports the stay, in the fore and aft direction below the passage and a vertical wall formed to stand upright at a position more outboard than the side edge of the opening, the frame being fixed to the roof such that a flange portion depending from the side edge of the opening is received between the vertical wall and an outboard one of the guide walls, and the support bracket has a U-shaped cross section opened upward, is disposed to receive the flange portion, supports the second seal member on an inboard side thereof, and is attached to the vertical wall on an outboard side thereof. a frame configured to be disposed below the roof so as to be aligned with the opening; a rear panel secured to the frame to close a rear portion of the opening; and a front panel that includes a stay depending from a side portion thereof and is supported by the frame via the stay so as to be slidable between a closed position to close a front portion of the opening and an open position where the front panel overlaps on top of the rear panel to open the front portion of the opening, wherein the rear panel includes a rear panel main body and a rear molded part provided on an outer peripheral edge of the rear panel main body and contacts an edge of the opening via a rear seal portion, the rear seal portion includes a first seal member mounted to the rear molded part in a rear portion of the opening and a second seal member extending in a fore and aft direction and supported by the frame via a support bracket to form a passage for the stay between the second seal member and the rear molded part in a side portion of the opening, characterised in that the frame includes a pair of guide walls (41A, 41B) disposed more inboard than a side edge of the opening and slidably guiding a slider, which supports the stay, in the fore and aft direction below the passage and a vertical wall formed to stand upright at a position more outboard than the side edge of the opening, the frame being fixed to the roof such that a flange portion depending from the side edge of the opening is received between the vertical wall and an outboard one of the guide walls, and the support bracket has a U-shaped cross section opened upward, is disposed to receive the flange portion, supports the second seal member on an inboard side thereof, and is attached to the vertical wall on an outboard side thereof.