Disclosed is a tail yarn cutting device for a spinning machine in which a tail yarn cutting member is provided on a blade so as to be capable of ascending and descending, with the tail yarn cutting member being constantly urged toward a spindle base by a coil spring. The tail yarn cutting member and the spindle base portion are equipped with a plurality of protrusions and recesses capable of being engaged with each other. In a state in which a roll or less or yarn is wound at a position somewhat below the portion where the tail yarn cutting member and the spindle base portion are in contact with each other, cop is pulled up by a doffing device, and the tail yarn cuttingmember is raised together with the cop halfway through the pulling-up, the yarn connected from the cop to a traveler being guided to a position between the tail yarn cutting member and the spindle base portion. Thereafter, the yarn is grasped between the tail yarn cutting member detached from the cop and the spindle base portion 5b, and the yarn is cut by a cutter portion.