A linear motion guide unit prevents damage to a corner portion of an end surface of a carriage resulting from high-speed rolling of the rolling elements, and eliminates the need for strict dimensional management of facing end surfaces of the carriage and a spacer. A crowning is formed at an end portion of the carriage, and an R chamfered portion is formed at a corner of an end surface of the carriage. An R chamfered portion is formed at a corner of the end surface of the spacer. The R chamfered portions define a valley portion between the facing surfaces of the carriage and the spacer. The rolling elements roll above the valley portion while striding it to thereby be prevented from colliding against the corner portion of the end surface of the carriage, whereby damage to the corner portion of the end surface of the carriage can be prevented.