Method for manufacturing glass fiber strand

Provided is a method for manufacturing a glass fiber strand in which a glass fiber strand is formed by bundling a plurality of glass fiber filaments comprising molten glass drawn out from a nozzle, wherein said method for manufacturing a glass fiber strand is capable of detecting breakage of the glass fiber filaments in a more reliable manner. This method comprises: an image capturing step for generating a plurality of items of image data by continuously capturing images of a plurality of glass fiber filaments f; an image processing step for extracting, from the image data, a high luminance object having a luminance of a prescribed value or more; and a breakage detection step for detecting that a glass fiber filament f has broken on the basis of the results of the image processing in the image processing step.