New and useful method of building a boiler frame significantly reduces the use of high load-lifting height crane and improves the operation efficiency despite bad weather. Multiple levels of steel supporting posts, which are established beforehand, are linked together with their top portion by beams and the 9th floor unit is fixed to the posts at an intermediate floor position temporarily. Suspension rods, which are suspended from lifting jacks, are then connected to the 8th floor unit and jacked up, while floor units made for lower than the 8th floor are connected on the ground to form a multi-floor unit. After connecting the multi-floor unit to the 9th floor unit the temporary fixation is released, the multi-floor unit is lifted up, and each floor unit is permanently fixed to the designated floor position repeatedly and respectively.