A spun yarn take-up system, comprising: a plurality of spun yarn take-up devices arranged in line in a predetermined direction; a yarn threading robot including a sucking retaining unit capable of suction-retaining a yarn and configured to be movable in the predetermined direction and be capable of performing yarn threading operation to each of the spun yarn take-up devices; and a yarn waste unit where the yarn sucked by the sucking retaining unit is wasted, a coupling device (9, 10) with a first coupler (73, 83) and a second coupler (74, 84), the coupling device (9, 10) configured to connect the first coupler (73, 83) and the second coupler (74, 84) by moving one coupler (74, 84) of the first coupler (73, 83) and the second coupler (74, 84) to the other coupler (73, 83) of the first coupler (73, 83) and the second coupler (74, 84), the first coupler (73, 83) including a first cylinder body, the second coupler (74, 84) including a second cylinder body facing the first cylinder body, a cylindrical ring member engaged on an outer side of the second cylinder body with a gap, and movable in an axial direction of the second cylinder body, a seal ring arranged between the second cylinder body and the ring member, and a bias mechanism biasing the ring member toward the first cylinder body, a sealing member being disposed on at least one of an end face of the first cylinder body and an end face of the ring member, and when the one coupler (74, 84) is moved toward the other coupler (73, 83), the end face of the first cylinder body contacting the end face of the ring member via the sealing member, whereby an inner passage of the first cylinder body is in communication with an inner passage of the second cylinder body, and the coupling device being provided on a waste yarn passage extending from the sucking retaining unit to the yarn waste unit. a yarn threading robot including a sucking retaining unit capable of suction-retaining a yarn and configured to be movable in the predetermined direction and be capable of performing yarn threading operation to each of the spun yarn take-up devices; and a yarn waste unit where the yarn sucked by the sucking retaining unit is wasted, a coupling device (9, 10) with a first coupler (73, 83) and a second coupler (74, 84), the coupling device (9, 10) configured to connect the first coupler (73, 83) and the second coupler (74, 84) by moving one coupler (74, 84) of the first coupler (73, 83) and the second coupler (74, 84) to the other coupler (73, 83) of the first coupler (73, 83) and the second coupler (74, 84), the first coupler (73, 83) including a first cylinder body, the second coupler (74, 84) including a second cylinder body facing the first cylinder body, a cylindrical ring member engaged on an outer side of the second cylinder body with a gap, and movable in an axial direction of the second cylinder body, a seal ring arranged between the second cylinder body and the ring member, and a bias mechanism biasing the ring member toward the first cylinder body, a sealing member being disposed on at least one of an end face of the first cylinder body and an end face of the ring member, and when the one coupler (74, 84) is moved toward the other coupler (73, 83), the end face of the first cylinder body contacting the end face of the ring member via the sealing member, whereby an inner passage of the first cylinder body is in communication with an inner passage of the second cylinder body, and the coupling device being provided on a waste yarn passage extending from the sucking retaining unit to the yarn waste unit.