Reliability of a semiconductor device is improved. In a flatness inspection of BGA (semiconductor device), there is formed a flatness standard where a permissible range in the direction of (+) of flatness at normal temperature is smaller than a permissible range in the direction of (−). With use of the above flatness standard, a flatness inspection of the semiconductor device at normal temperature is performed to determine whether the mounted item is non-defective or defective. With the above process, defective mounting caused by a package warp when heated during reflow soldering etc. is reduced and reliability of BGA is improved. At the same time, flatness management of a substrate-type semiconductor device with better consideration of a mounting state can be performed.