To improve shielding ability from an external environment, load capacity, buffering ability, and maintenance ability in a support structure of a caster.

This support structure 1 of a caster comprises a slide shaft 7 that is fixed to the caster 3 and slides vertically with the caster 3, a support easing 9 that is fixed to a mounting part 5 of the caster 3 and allows sliding of the slide shaft 7 in a certain range, buffering mechanism 11 that is disposed between the slide shaft 7 and the support casing 9 and absorbs vibration and impact in the sliding direction to the slide shaft 7, and a sealing means that is provided in or near a sliding part between the slide shaft 7 and the support casing 9 and shields flow-in and flow-out of material between the inside and outside of the mounting part 5 of the caster 3.