A miniature linear motion guide unit is described in which a tubular member for a return passage is installed in an outward open recess cut in the carriage and a covering to bear the tubular member is integral with an end cap major part. This construction helps make the slider compact with cost saving in production. The slider is composed of a carriage made up of an upper portion and side bulges extending downward and having the outward open recesses, end caps having turnaround passages, the tubular members lying on outsides of the side bulges of the carriage, and coverings connected integrally with the end cap major parts to embrace the tubular members in combination with the outsides of the carriage.