To cut in advance a string such that the terminal 1x of the first string 1a and the beginning 1y of the second string 1b are not too long at a knot 120.

A string selecting apparatus 30 which is to supply a string 1 successively by holding it at plural string-holding parts 32, is fixed switchably at a position facing a string supplying position A and a string knotting position B which are in a string knotting area and at a sheltering position which is in a distant side from the first position. In the sheltering position, a cutter blade 38 which is to cut the beginning of a string coming out into a predetermined length, is fixed on the inner side of a cutter cover 37. On the cutter cover 37, a cutter gutter 37a which is to guide a string 1 to the cutter blade 38, is made.