A bike carrier used in an apparatus for fixing a bike disposed on a vehicle roof, the bike carrier comprising: a roof rack module including a first roof rack extending in a first direction, a second roof rack spaced apart from the first roof rack while facing the first roof rack, a third roof rack extending in a second direction perpendicular to the first direction and intersecting the first and second roof racks (110, 120), and a fourth roof rack spaced apart from the third roof rack while facing the third roof rack and intersecting the first and second roof racks (110, 120); a frame fixing module including a housing coupled to the first roof rack to move in the first direction along the first roof rack, and a holding arm connected to the housing and rotated clockwise or counterclockwise about the second direction to fix a frame of the bike; and a tire fixing module (410, 420) disposed on the second roof rack to fix a tire of the bike, wherein the tire fixing module (410, 420) includes: a first tire fixing module and a second tire fixing module, the first and second tire fixing modules and being disposed on the second roof rack and move in a direction along the second roof rack, the bike carrier comprising a first sliding module disposed between the third roof rack and the second roof rack, to couple the third roof rack and the second roof rack and movable along the third roof rack, a second sliding module disposed between the fourth roof rack and the second roof rack, to couple the fourth roof rack and the second roof rack and movable along the fourth roof rack, wherein the second roof rack is movable along the third roof rack and the fourth roof rack through the first sliding module and the second sliding module, wherein in a state in which the first sliding module is installed on the third roof rack, the second roof rack is coupled to the first sliding module, wherein in a state in which the second sliding module is installed on the fourth roof rack, the second roof rack is coupled to the second sliding module, characterised by a mounting space formed between rollers (521, 522) of the first sliding module, the second roof rack being coupled to the first sliding module through the mouting space, and by a mounting space formed between rollers (521, 522) of the second sliding module, the second roof rack being coupled to the second sliding module through the mounting space.. a roof rack module including a first roof rack extending in a first direction, a second roof rack spaced apart from the first roof rack while facing the first roof rack, a third roof rack extending in a second direction perpendicular to the first direction and intersecting the first and second roof racks (110, 120), and a fourth roof rack spaced apart from the third roof rack while facing the third roof rack and intersecting the first and second roof racks (110, 120); a frame fixing module including a housing coupled to the first roof rack to move in the first direction along the first roof rack, and a holding arm connected to the housing and rotated clockwise or counterclockwise about the second direction to fix a frame of the bike; and a tire fixing module (410, 420) disposed on the second roof rack to fix a tire of the bike, wherein the tire fixing module (410, 420) includes: a first tire fixing module and a second tire fixing module, the first and second tire fixing modules and being disposed on the second roof rack and move in a direction along the second roof rack, the bike carrier comprising a first sliding module disposed between the third roof rack and the second roof rack, to couple the third roof rack and the second roof rack and movable along the third roof rack, a second sliding module disposed between the fourth roof rack and the second roof rack, to couple the fourth roof rack and the second roof rack and movable along the fourth roof rack, wherein the second roof rack is movable along the third roof rack and the fourth roof rack through the first sliding module and the second sliding module, wherein in a state in which the first sliding module is installed on the third roof rack, the second roof rack is coupled to the first sliding module, wherein in a state in which the second sliding module is installed on the fourth roof rack, the second roof rack is coupled to the second sliding module, characterised by a mounting space formed between rollers (521, 522) of the first sliding module, the second roof rack being coupled to the first sliding module through the mouting space, and by a mounting space formed between rollers (521, 522) of the second sliding module, the second roof rack being coupled to the second sliding module through the mounting space..