Abstract: A gas-permeable seamless pipe structure formed in a pipe shape by a wet process comprising (A) 20 to 95% by weight of thermoplastic fibers and (B) 5 to 80% by weight of a component consisting of (a) 20 to 100% of other fibers being infusible at the fusing temperature of said thermoplastic fibers (A) or having a higher melting point than said thermoplastic fibers (A) and (b) 0 to 80% by weight of a void-containing particulate material having an apparent density of not more than 1 and an average particle size of 20 to 2,000 microns and being infusible at the fusing temperature of said thermoplastic fibers (A), said thermoplastic fibers (A) being bonded to the other component (B) as a result of heat fusing; a method for producing the pipe structure; and an apparatus for use in this method. The pipe structure has superior physical properties such as strength and hardness, good water resistance, light weight and superior gas-permeability.