A method of manufacturing a heat transport device includes injecting a working fluid that transports heat by a phase change into a casing through an injection opening of the casing under reduced pressure, sealing an injection path by caulking under the reduced pressure, the injection path being provided in the casing into which the working fluid is injected and causing the injection opening and an action area in which the phase change of the working fluid occurs to communicate with each other, contacting a peripheral area of the injection opening of the casing with an inner surface of the injection path by caulking the peripheral area, the peripheral area including the injection opening, and sealing the injection opening by welding a part of the casing contacted.