A lubrication structure of a planetary gear set includes a hollow shaft on which the planetary gear set is disposed and forming an oil passage in an axial direction thereof and a plurality of oil holes in a radial direction thereof to supply a lubrication oil to the planetary gear set, and an internal pipe provided within the oil passage of the hollow shaft, wherein a gap chamber is formed between the internal pipe and the hollow shaft with a preset gap, where a plurality of oil supply holes are formed through the internal pipe in the radial direction to fluidically communicate the gap chamber and an internal space of the internal pipe.