Fastening device and lace tightening and releasing method

A lace tightening and releasing method, comprising:

• a fastening step, a fastening device disposed at an article being operated, the fastening device comprising a case, a spool, a plurality of ratchet teeth, an incremental releasing set and a knob, the spool being coupled to a lace and located within the case, the incremental releasing set comprising a ratchet element and a swinging arm, wherein as the knob is rotated in a tightening direction, a ratchet arm of the ratchet element is disengaged from at least one of the ratchet teeth to allow the spool to fasten the lace;
• an incremental releasing step, the swinging arm of the fastening device being operated, the swinging arm moving a linking portion of the ratchet element, the ratchet arm being disengaged from at least one of the ratchet teeth and the incremental releasing set being engaged with at least another one of the ratchet teeth, thereby allowing the spool to rotate in a releasing direction to release one segment of the lace;
• and
• a full releasing step, the knob being pulled up without operating the swinging arm first to allow the ratchet arm of the fastening device not to prohibit the spool from rotating in the releasing direction, thereby allowing the lace to be freely released.