A motion snubbing device using an inertia mass, which is disposed within a housing and supported for free rotation on a shaft which is rotated with relative motion of telescoped support members. A spring plate is secured to the shaft and faces one end of the inertia member. A plurality of torque transmission balls are each interposed between each of recesses formed in the plate member near the periphery thereof and each of recesses formed in the corresponding end face of the inertia mass at corresponding positions. The plate is provided on its side opposite its recesses and near its periphery with brake shoes, and the housing has a frictional surface facing and adapted to cooperate with these brake shoes.