A linear motion guide unit is provided in which a crowning portion available extensively for standard specification is made easily. The crowning portion is comparatively small in depth, and rich in high accuracy and high durability. A raceway groove for a load race in a carriage is made at an ingress/egress area thereof with the crowning portion of a curved profile that varies gently to allow the rolling element to move in and out of the load race with smoothness. The carriage is provided at the forward and aft ends of the raceway groove with rounded bevels, which are made in a curved contour merging into the associated crowning portion without causing any discontinuity at a junction of the rounded bevel with the crowning portion.