A reduction component is linked to the output shaft of a hydraulic motor, and reduces the rotational speed of the hydraulic motor. A housing component has a rotation-side housing that is rotated around a horizontal rotational axis by the rotation of the hydraulic motor whose speed has been reduced by the reduction component, and a stationary-side housing that rotatably supports the rotation-side housing. The housing component houses the reduction component. A sealing component is disposed inside a gap between the rotation-side housing and the stationary-side housing, and seals the gap. An oil splasher splashes up lubricating oil to provide the lubricating oil to the upper part of the sealing component. The oil splasher has a plurality of concave components formed in the portion of the rotation-side housing facing a seal disposition space in which the sealing component is disposed.