The present invention relates to a sliding device, comprising: a rail body which is disposed at both sides of a sliding object, and which has an open bottom and an interior with a space; a movable side roller which is disposed at both edges of the space diagonally facing each other, and which rolls in contact with the rail body; a fixed side rail body which is disposed at a fixed object and beneath the overlapped lower portion of the rail body, and which has an open top and an interior with a locking space; a fixed side roller which is disposed at both edges of the locking space diagonally facing each other, and which rolls in contact with the fixed side rail body; and a sliding unit which is connected to the space and the locking space, and has a top roll-contacting the movable side roller and a bottom roll-contacting the fixed side roller. The movable side rollers face each other such that the angle from the line ranging from the center of the sliding unit to the sliding object, to the line interconnecting the centers of the movable side rollers facing each other, is 40 to 50 degrees. The fixed side rollers face each other such that the angle from the line ranging from the center of the sliding unit to the sliding object, to the line interconnecting centers of the fixed side rollers facing each other, is 130 to 140 degrees.