To reduce construction cost and to improve safety by providing a building method for an air-inflated membrane structural member without using a heavy machinery such as a crane, etc.

A building method for an air-inflated membrane structural member at the time of construction of an air-inflated membrane structure includes a process to set an air bag 1 which is a bag body below a tube membrane 2 which is an air membrane, a process to lift up the tube membrane 2 by expanding the air bag 1, a process to make a tube membrane structural member 2' as the air-inflated membrane structural member by filling air in the tube membrane 2 and a process to contract the air bag and remove it.