A linear motion guide unit is described that allows seal attachment to be performed highly accurately and easily as well as preventing dislocation of the seals after attachment. Said effects are obtained by providing projections and slots in a slider and seals and mutually engaging these projections and slots. In addition, a linear motion guide unit is described that allows lubricant to be supplied both quickly and easily without having to disassemble the linear motion guide unit even when small in size. Said effect is obtained by forming lubricant injection holes in the seals and injecting a lubricant such as grease through said lubricant injection holes with a lubricant injector.