A structure for supporting a slip joint in which the slip joint serves to support a vehicle webbing in such a manner that the webbing is movable in the lengthwise direction of the vehicle and is pivotally supported by a support member attached to a vehicle body, so that an extension of a line running in a direction of a resultant force of a webbing takeup force and a webbing pulling-out force passes through the portion where the slip joint is pivotally supported by the support member. The moment which is produced by the resultant force and which acts on the slip joint is therefore eliminated or reduced.