NOVELTY - An austenitic stainless steel welded pipe comprises (in %mass) carbon (0.15 or less), nitrogen (0.25 or less), silicon (4.0 or less), manganese (3.0 or less), phosphorus (0.10 or less), sulfur (0.03 or less), nickel (6-20), chromium (14-28) and remaining iron and unavoidable impurity. The area ratio of delta -ferrite phase of the welded portion in the welded pipe is 0.5% or less. The amount (M) of carbon, nitrogen, silicon, manganese, nickel, copper, chromium and molybdenum satisfying preset relation is less than -100.    USE - Austenitic stainless steel welded pipe used for high pressure hydrogen transport in fuel cells for motor vehicles.    ADVANTAGE - The austenitic stainless steel welded pipe has excellent hydrogen embrittlement resistance, corrosion resistance, stress corrosion crack resistance and enables efficient transport of 40 MPa high pressure hydrogen.    DETAILED DESCRIPTION - An austenitic stainless steel welded pipe comprises (in %mass) carbon (0.15 or less), nitrogen (0.25 or less), silicon (4.0 or less), manganese (3.0 or less), phosphorus (0.10 or less), sulfur (0.03 or less), nickel (6-20), chromium (14-28) and remaining iron and unavoidable impurity. The area ratio of delta -ferrite phase of the welded portion in the welded pipe is 0.5% or less. The amount (M) of carbon, nitrogen, silicon, manganese, nickel, copper, chromium and molybdenum is less than -100 and the amount (D) of chromium, silicon, niobium, molybdenum, nickel, manganese, copper, carbon and nitrogen is 6-10. The M and D values are calculated using the formulae: M=551-462(C+N)-9.2Si-8.1Mn-29(Ni+Cu)-13.7Cr-18.5Mo and D=(Cr+1.5Si+0.5Nb+Mo)-(Ni+0.5Mn+0.3Cu+30C+30N). An INDEPENDENT CLAIM is included for manufacture of the austenitic stainless steel welded pipe.    DESCRIPTION OF DRAWING(S) - The drawing shows the external appearance of the welded pipe.    Base material (1)    Welded bead (2)    Welding portion cross section (3)    Weld metal (4)    Base material welding interface (5)