Disclosed are a structure of a composite flexible pipeline for crude oil and natural gas transportation, a laying method therefor, and a transportation method for crude oil or natural gas. The transportation method is a method for transporting crude oil or natural gas through a pipeline comprising a multilayer structure having at least one barrier resin layer. The barrier resin layer comprises an ethylene-vinyl alcohol copolymer resin as a main component. A pipeline for the transportation method, and a laying method for the pipeline. Through a pipeline which does not have corrosion concern and has excellent acid resistance and acid gas barrier properties, a method for safely transporting crude oil or natural gas is provided without leak of hydrogen sulfide gas, carbon dioxide, and hydrocarbon gas to the external environment.