An object of the present invention is to develop: a method of efficiently producing a long bagworm silk thread containing no contaminant while preventing a change in the spinning direction and the runaway of the bagworm from a rail, and alleviating a burden on the bagworm; and an apparatus for implementing the thread-producing method. Provided is an apparatus for producing a bagworm silk thread, having a movable rail having a width smaller than the maximum width between the right and left legs of a bagworm and configured to move in the longitudinal direction and to be able to hold with the legs of the bagworm; and a fixator configured to fix a bagworm, wherein the fixator is placed at a position such that the fixed bagworm can hold the movable rail.