To positively prevent a pressure medium sealed into an outer tube from leaking out from a clearance relative to an oil damper, there is provided a seal construction of a shock absorber 1 with leveling function wherein a seal mechanism 3 is disposed in an outer tube 2 to slidably insert a shock absorber 4 thereinto, a piston rod 5 extending from the shock absorber 4 is connected on the outer tube 2 side, a pressure medium sealed into the outer tube 2 is heated by a heating means 7 and leveling is carried out while controlling the support force exerting on the shock absorber 4, the seal construction being constituted that a free piston 15 is interposed opposite to the seal mechanism 3 between the outer tube 2 and the shock absorber 4, and the seal mechanism 3 and the free piston 15 compart and form a lubricating oil chamber 16 therebetween whereas the free piston 15 is always biased toward the lubricating oil chamber 16.