A yarn producing apparatus for producing carbon nanotube yarn by aggregating carbon nanotube fibers, the yarn producing apparatus comprising: a substrate support configured to support a carbon nanotube forming substrate; a continuous drawing unit configured to continuously draw the carbon nanotube fibers from the carbon nanotube forming substrate; a yarn producing unit configured to aggregate the carbon nanotube fibers drawn by the continuous drawing unit; a substrate replacing mechanism configured to replace the carbon nanotube forming substrate supported on the substrate support with another carbon nanotube forming substrate, characterized in that the substrate replacing mechanism includes a substrate replacing unit configured to replace the carbon nanotube forming substrate supported on the substrate support with another carbon nanotube forming substrate, and a controller configured to control the substrate replacing unit such that the carbon nanotube forming substrate supported on the substrate support is replaced with another carbon nanotube forming substrate, wherein the substrate replacing mechanism further includes a remaining amount monitor configured to monitor the remaining amount of the carbon nanotube fibers in the carbon nanotube forming substrate supported by the substrate support, and the controller controls the substrate replacing unit such that the carbon nanotube forming substrate supported on the substrate support is replaced with another carbon nanotube forming substrate, based on a result of monitoring by the remaining amount monitor. a substrate support configured to support a carbon nanotube forming substrate; a continuous drawing unit configured to continuously draw the carbon nanotube fibers from the carbon nanotube forming substrate; a yarn producing unit configured to aggregate the carbon nanotube fibers drawn by the continuous drawing unit; a substrate replacing mechanism configured to replace the carbon nanotube forming substrate supported on the substrate support with another carbon nanotube forming substrate, characterized in that the substrate replacing mechanism includes a substrate replacing unit configured to replace the carbon nanotube forming substrate supported on the substrate support with another carbon nanotube forming substrate, and a controller configured to control the substrate replacing unit such that the carbon nanotube forming substrate supported on the substrate support is replaced with another carbon nanotube forming substrate, wherein the substrate replacing mechanism further includes a remaining amount monitor configured to monitor the remaining amount of the carbon nanotube fibers in the carbon nanotube forming substrate supported by the substrate support, and the controller controls the substrate replacing unit such that the carbon nanotube forming substrate supported on the substrate support is replaced with another carbon nanotube forming substrate, based on a result of monitoring by the remaining amount monitor. a substrate replacing unit configured to replace the carbon nanotube forming substrate supported on the substrate support with another carbon nanotube forming substrate, and a controller configured to control the substrate replacing unit such that the carbon nanotube forming substrate supported on the substrate support is replaced with another carbon nanotube forming substrate, wherein the substrate replacing mechanism further includes a remaining amount monitor configured to monitor the remaining amount of the carbon nanotube fibers in the carbon nanotube forming substrate supported by the substrate support, and the controller controls the substrate replacing unit such that the carbon nanotube forming substrate supported on the substrate support is replaced with another carbon nanotube forming substrate, based on a result of monitoring by the remaining amount monitor.