An air bearing slider of a disk drive for moving a read/write head to a desired position on a disk by being lifted above a surface of the disk includes a body having a surface facing the disk. A first rail base protrudes from the surface of the body facing the disk and has a U shape open to a trailing end portion of the body. A first positive pressure generating rail portion protrudes from the first rail base and includes a cross rail separated from a leading end portion of the first rail base and extending in a first direction perpendicular to a direction in which air enters and a pair of side rails extending from both ends portion of the cross rail in a second direction parallel to the direction in which air enters. A negative pressure cavity is defined by the first rail base. A second rail base protrudes from the surface of the body facing the disk adjacent to the trailing end portion of the body. A second positive pressure generating rail portion protrudes from the second rail base. A negative pressure-generating pocket is formed in each of the side rails and separate from the negative pressure cavity and open to the outside of the side rails.