A conveyor comprising: a carrying member adapted to carry an object to be conveyed; a plurality of rollers arranged under the carrying member and adapted to be guided to move along guide rails in a first direction; and a first magnetic engaging portion arranged to extend from a lower surface of the carrying member to a position near to the guide rails in a second direction normal to the first direction and adapted to interact with a second magnetic engaging portion on the guide rails, to generate a driving force for driving the conveyor in the first direction; wherein the first magnetic engaging portion comprises: a first set of magnetic racks; the conveyor being characterized in that the first magnetic engaging portion further comprises a second set of magnetic racks arranged opposite to the first set of magnetic racks at a predetermined distance (d) from the first set of magnetic racks such that the second magnetic engaging portion is locatable between the first set of magnetic racks and the second set of magnetic racks; wherein the first magnetic engaging portion further comprises: a connecting element fixed on the lower surface of the carrying member; and a pair of first supporting members connected to the connecting element and adapted to support the first set of magnetic racks and the second set of magnetic racks respectively. a carrying member adapted to carry an object to be conveyed; a plurality of rollers arranged under the carrying member and adapted to be guided to move along guide rails in a first direction; and a first magnetic engaging portion arranged to extend from a lower surface of the carrying member to a position near to the guide rails in a second direction normal to the first direction and adapted to interact with a second magnetic engaging portion on the guide rails, to generate a driving force for driving the conveyor in the first direction; wherein the first magnetic engaging portion comprises: a first set of magnetic racks; the conveyor being characterized in that the first magnetic engaging portion further comprises a second set of magnetic racks arranged opposite to the first set of magnetic racks at a predetermined distance (d) from the first set of magnetic racks such that the second magnetic engaging portion is locatable between the first set of magnetic racks and the second set of magnetic racks; wherein the first magnetic engaging portion further comprises: a connecting element fixed on the lower surface of the carrying member; and a pair of first supporting members connected to the connecting element and adapted to support the first set of magnetic racks and the second set of magnetic racks respectively. a first set of magnetic racks; the conveyor being characterized in that the first magnetic engaging portion further comprises a second set of magnetic racks arranged opposite to the first set of magnetic racks at a predetermined distance (d) from the first set of magnetic racks such that the second magnetic engaging portion is locatable between the first set of magnetic racks and the second set of magnetic racks; wherein the first magnetic engaging portion further comprises: a connecting element fixed on the lower surface of the carrying member; and a pair of first supporting members connected to the connecting element and adapted to support the first set of magnetic racks and the second set of magnetic racks respectively. a connecting element fixed on the lower surface of the carrying member; and a pair of first supporting members connected to the connecting element and adapted to support the first set of magnetic racks and the second set of magnetic racks respectively.