A yarn processor capable of processing a yarn unwound from a yarn supply package (Ps) and winding the yarn onto a winding bobbin (Bw), comprising: a yarn supply package retaining portion which is configured to retain the yarn supply package (Ps); a winding device which is capable of forming a wound package (Pw) by winding the yarn onto the winding bobbin (Bw); a cutting unit which is capable of cutting the yarn before the yarn is wound onto the winding bobbin (Bw); a bobbin replacement unit which is capable of replacing the wound package (Bw) formed by the winding device with a new winding bobbin (Bw4, Bw5) as the winding bobbin (Bw) and which is capable of performing yarn threading to the new winding bobbin (Bw4, Bw5); and a controller which is capable of performing: a formation termination process of cutting the yarn by controlling the cutting unit and terminating formation of the wound package (Pw) by controlling the winding device; and a replacement process of replacing the formed wound package (Pw) with the new winding bobbin (Bw4, Bw5) and threading a yarn to the new winding bobbin (Bw4, Bw5) by controlling the bobbin replacement unit, the controller performing the formation termination process and the replacement process when determining that an amount of the yarn in the wound package (Pw) in formation reaches a predetermined target wound amount, the control unit generating, by calculation, remaining amount-related information that is numerical information regarding a remaining amount of the yarn remaining in the yarn supply package (Ps) which is retained by the yarn supply package retaining portion and from which the yarn is being unwound, and when determining in remaining amount reduction determination that a numerical value of the remaining amount-related information is not larger than a predetermined value, the control unit performing the formation termination process to cause the winding device to form a formation forcible termination wound package (Pw3s) that is a wound package (Pw) having a smaller amount of the yarn than the target wound amount. a yarn supply package retaining portion which is configured to retain the yarn supply package (Ps); a winding device which is capable of forming a wound package (Pw) by winding the yarn onto the winding bobbin (Bw); a cutting unit which is capable of cutting the yarn before the yarn is wound onto the winding bobbin (Bw); a bobbin replacement unit which is capable of replacing the wound package (Bw) formed by the winding device with a new winding bobbin (Bw4, Bw5) as the winding bobbin (Bw) and which is capable of performing yarn threading to the new winding bobbin (Bw4, Bw5); and a controller which is capable of performing: a formation termination process of cutting the yarn by controlling the cutting unit and terminating formation of the wound package (Pw) by controlling the winding device; and a replacement process of replacing the formed wound package (Pw) with the new winding bobbin (Bw4, Bw5) and threading a yarn to the new winding bobbin (Bw4, Bw5) by controlling the bobbin replacement unit, the controller performing the formation termination process and the replacement process when determining that an amount of the yarn in the wound package (Pw) in formation reaches a predetermined target wound amount, the control unit generating, by calculation, remaining amount-related information that is numerical information regarding a remaining amount of the yarn remaining in the yarn supply package (Ps) which is retained by the yarn supply package retaining portion and from which the yarn is being unwound, and when determining in remaining amount reduction determination that a numerical value of the remaining amount-related information is not larger than a predetermined value, the control unit performing the formation termination process to cause the winding device to form a formation forcible termination wound package (Pw3s) that is a wound package (Pw) having a smaller amount of the yarn than the target wound amount.