A string-guiding structure for a curtain-reeling device substantially has a string-guiding frame mounted at an entrance of a string-guiding wheel assembly to limit the string extended from the curtain-reeling device inside the string-guiding frame and to be wound on the string-guiding wheel assembly when the string is released or collected. Therefore, the string-guiding frame depresses the oscillation and swing of the string during operation to avoid the string being jammed in the gaps of the string-guiding wheel assembly.