A six-row ball bearing linear guideway is provided with six rows of balls disposed between the slider and the rail. The six rows of balls are symmetrically disposed at two sides of the rail, the balls in the middle and upper rail rolling grooves bear and increase the load capacity in the downward direction. The balls in the lower rail rolling grooves bear a load in the upward direction, and the profile factor of the lower rail rolling grooves is smaller than that of the upper rail rolling grooves, thus the rated static load capacity in the upward direction is improved. The balls in the upper, middle and lower rail rolling grooves all serve to bear the load capacity in the lateral direction, thus the rated static load capacity in the lateral direction is improved. Hence, the rated static load capacity is improved in upward, downward and lateral directions.