In a sun roof system, a panel bracket (13) attached to a sun roof panel (11) is provided with a guide slot (14) having a prescribed profile and extending in a fore-and-aft direction, and is slidably supported on a guide rail (21) by a front slider (15) and a rear slider (16). The rear slider is provided with a pin (17c) engaged by the guide slot. The panel bracket is also provided with a front cam piece (41) and a rear cam piece (42) slidably supported by the guide rail. The guide rail is provided with a horizontal main cam groove (21b, 21d), a front cam groove (43) for smoothly guiding the front cam piece into and out of the main cam groove and a rear cam groove for smoothly guiding the rear cam piece into and out of the main cam groove. The cooperation between the front and rear cam pieces and the front and rear cam grooves, respectively, is effective in preventing the undesired fore-and-aft movement of the sub roof panel not only when the sun roof is fully closed but also when tiling up and tiling down the sun roof panel.