To provide a condensation prevention tool for a sash capable of inexpensively and efficiently preventing the indoor side surface of the sash from being condensed in winter by making an enclosed air layer formed between the indoor side surface and the panel of the sash function as a heat-insulated layer.

This condensation prevention tool for a sash is attached to the sash 2 and prevents the indoor side surface of the sash 2 from being condensed. The tool includes the panel 11 is disposed in such a manner as to form a space 12 along the indoor side surface of the sash 2. The enclosed air layer is formed by surrounding the peripheral edge of the space 12.