Provided is a linear motion guide device capable of maintaining high dustproof performance over a long period. A linear motion guide device (1) is provided with a side seal unit (10) attached to an axial end of a slider (3). The side seal unit (10) is provided with: a first seal member (11) and a second seal member (14) which are arranged along the axis of the slider (3), the first seal member (11) being located on the slider (3) side, the second seal member (14) being located on the outer side in the direction of the axis of the slider (3); and a lubrication member (17) sandwiched and held between the first seal member (11) and the second seal member (14). The first seal member (11) is provided with first lip sections (12c) in sliding contact with rolling body rolling grooves (2a) of a guide rail (2). The second seal member (14) is provided with a second lip section (15c) in sliding contact with the rolling body rolling grooves (2a). The lubrication member (17) is provided with a first oil containing body (18) for supplying a lubricating agent to the rolling body rolling grooves (2a). The first lip sections (12c) and the second lip sections (15c) are arranged so as not to make contact with the first oil containing body (18).