To provide a long material cutting method which reduces load on a computer, does not disturb rolling of a bar, and cuts the bar so as to shorten the length of a waste portion of the bar.

When the plurality of long materials are simultaneously cut, a maximum number of the long materials to be simultaneously cut within a cutting allowable range is determined at every line successively flowing through rolling lines, based on billet charging information. Then an accumulated surplus length for every number of collectible short materials, is calculated for a plurality of adoptable short length candidates, based on an as-rolled length L and a specified length of the long material, and the adoptable short length that produces a minimum accumulated surplus length is determined as the short length.