To make a continuous welding of a heat-weldable paper band possible by rapidly recovering the temperature of a heater which descends by the welding motion.

This band tying device BN places a band B on an article to be tied, tightens the band, heat-welds a superposed section of the band, cuts the band in the vicinity of the heat-welded section, and separates the band from the feeding source. In such a band tying device BN, a mechanism which heat-welds the band is equipped with the heater 35. At the same time, the band tying device is constituted in such a manner that a power feeding configuration to the heater after a welding motion can be temporarily changed for each welding motion.