A roof apparatus for a vehicle, comprising: a pair of guide rails (14, 15) extending in a front/rear direction of the vehicle along side end portions of an opening portion formed on a roof of a vehicle; a movable panel supported by the pair of guide rails (14, 15) and opening and closing the opening portion by moving in the front/rear direction of the vehicle; a housing extending in a width direction of the vehicle along a front end portion of the opening portion, being connected to a front end portion of each of the pair of guide rails (14, 15) and supporting a drive mechanism; a casing (51, 52) at least part of which is constituted by the housing; a first spur tooth rack belt and a second spur tooth rack belt both of which are accommodated in the pair of guide rails (14, 15) and in the casing (51, 52) in a manner that the first spur tooth rack belt and the second spur tooth rack belt slide along the pair of guide rails (14, 15) and along the casing (51, 52) for transmitting a drive force of the drive mechanism to the movable panel; wherein the first spur tooth rack belt includes a plurality of first spur teeth formed on a surface of the first spur tooth rack belt which faces a surface of the second spur tooth rack belt on which a plurality of second spur teeth are formed in a manner that the plurality of first spur teeth and the plurality of second spur teeth protrude in a direction perpendicular to a lengthwise direction of the first spur tooth rack belt and the second spur tooth rack belt; the roof apparatus being characterised in that a slope portion constituting part of the casing (51, 52) and being inclined upward toward a rear side of the vehicle is provided forward of each of the pair of guide rails (14, 15) relative to the front/rear direction of the vehicle; a pair of guide portions (16, 22) is provided at each of the guide rails (14, 15), the guide portions (16, 22) positioned keeping a distance from each other in the width direction of the vehicle for guiding the first spur tooth rack belt and the second spur tooth rack belt respectively in the front/rear direction of the vehicle; each of the pair of guide portions (16, 22) includes a bottom wall portion (17, 23) and a pair of restricting wall portions (18, 19, 24, 25) positioned at side portions of the bottom wall portion (17, 23) relative to the width direction of the vehicle; and a front end portion of each of the pair of guide rails (14, 15) includes a cutout portion (45,46) formed by cutting out the bottom wall portion (17, 23), and the slope portion and each of the pair of guide portions (16, 22) are connected with each other in a manner that the slope portion communicates with each of the pair of guide portions (16, 22) via the cutout portion (45, 46). a pair of guide rails (14, 15) extending in a front/rear direction of the vehicle along side end portions of an opening portion formed on a roof of a vehicle; a movable panel supported by the pair of guide rails (14, 15) and opening and closing the opening portion by moving in the front/rear direction of the vehicle; a housing extending in a width direction of the vehicle along a front end portion of the opening portion, being connected to a front end portion of each of the pair of guide rails (14, 15) and supporting a drive mechanism; a casing (51, 52) at least part of which is constituted by the housing; a first spur tooth rack belt and a second spur tooth rack belt both of which are accommodated in the pair of guide rails (14, 15) and in the casing (51, 52) in a manner that the first spur tooth rack belt and the second spur tooth rack belt slide along the pair of guide rails (14, 15) and along the casing (51, 52) for transmitting a drive force of the drive mechanism to the movable panel; wherein the first spur tooth rack belt includes a plurality of first spur teeth formed on a surface of the first spur tooth rack belt which faces a surface of the second spur tooth rack belt on which a plurality of second spur teeth are formed in a manner that the plurality of first spur teeth and the plurality of second spur teeth protrude in a direction perpendicular to a lengthwise direction of the first spur tooth rack belt and the second spur tooth rack belt; the roof apparatus being characterised in that a slope portion constituting part of the casing (51, 52) and being inclined upward toward a rear side of the vehicle is provided forward of each of the pair of guide rails (14, 15) relative to the front/rear direction of the vehicle; a pair of guide portions (16, 22) is provided at each of the guide rails (14, 15), the guide portions (16, 22) positioned keeping a distance from each other in the width direction of the vehicle for guiding the first spur tooth rack belt and the second spur tooth rack belt respectively in the front/rear direction of the vehicle; each of the pair of guide portions (16, 22) includes a bottom wall portion (17, 23) and a pair of restricting wall portions (18, 19, 24, 25) positioned at side portions of the bottom wall portion (17, 23) relative to the width direction of the vehicle; and a front end portion of each of the pair of guide rails (14, 15) includes a cutout portion (45,46) formed by cutting out the bottom wall portion (17, 23), and the slope portion and each of the pair of guide portions (16, 22) are connected with each other in a manner that the slope portion communicates with each of the pair of guide portions (16, 22) via the cutout portion (45, 46).