A manufacturing method for a metal pipe for forming a metal plate into a metal pipe through a pipe manufacturing step, a welding step, and a sizing/reshaping step performed using forming tools, the manufacturing method using: a stand array line having a configuration in which some or each of the forming tools used in each of the steps is held in a corresponding stand across position adjusting means allowing position adjustment of the forming tool relative to a forming target metal plate (raw plate/raw pipe); storage means, after implementation of a step targeted for part or whole of the stand array line of conducting simulation analysis in advance on forming processes of forming from the metal plate into the metal pipe using the forming tool on the basis of different dimensions or types of various metal plates, and after implementation of a step of acquiring data about a correlation value at each or a particular forming tool stand in the line targeted for the analysis between a deformed shape value of the raw pipe in the vicinity of the stand or in the vicinity of the forming tool and positional information about the forming tool in each stand on the basis of result of the simulation analysis on the various types of forming processes, the storage means storing the various types of forming processes in advance as data about a correlation value according to various types of ideal models between a deformed shape value of the raw pipe and a forming tool position; and output means, by using calculation means that makes comparison with the data in the storage means and expects a forming process for the raw pipe on the basis of a deformed shape value of the raw pipe being formed that is measured through a step of measuring a deformed shape value of the raw pipe being formed using a measurement sensor during implementation of the analysis on the target, and information about the dimension or about the dimension and type of the forming target metal plate, the output means assuming a forming process unique to the raw pipe during implementation of the analysis on the target, selecting positional information about a forming tool necessary for the assumed forming process, and outputting positional information about a forming tool in the stand required to be adjusted in position. a stand array line having a configuration in which some or each of the forming tools used in each of the steps is held in a corresponding stand across position adjusting means allowing position adjustment of the forming tool relative to a forming target metal plate (raw plate/raw pipe); storage means, after implementation of a step targeted for part or whole of the stand array line of conducting simulation analysis in advance on forming processes of forming from the metal plate into the metal pipe using the forming tool on the basis of different dimensions or types of various metal plates, and after implementation of a step of acquiring data about a correlation value at each or a particular forming tool stand in the line targeted for the analysis between a deformed shape value of the raw pipe in the vicinity of the stand or in the vicinity of the forming tool and positional information about the forming tool in each stand on the basis of result of the simulation analysis on the various types of forming processes, the storage means storing the various types of forming processes in advance as data about a correlation value according to various types of ideal models between a deformed shape value of the raw pipe and a forming tool position; and output means, by using calculation means that makes comparison with the data in the storage means and expects a forming process for the raw pipe on the basis of a deformed shape value of the raw pipe being formed that is measured through a step of measuring a deformed shape value of the raw pipe being formed using a measurement sensor during implementation of the analysis on the target, and information about the dimension or about the dimension and type of the forming target metal plate, the output means assuming a forming process unique to the raw pipe during implementation of the analysis on the target, selecting positional information about a forming tool necessary for the assumed forming process, and outputting positional information about a forming tool in the stand required to be adjusted in position.