Factors that cause spreading of urban fires among buildings are flame contact, radiant heat, convective heat, and firebrands. There are many cases in which firespread is caused by leaping flames resulting from many firebrands in places that are distant from the fire outbreak site, especially under strong wind conditions. Firebrands and leaping flames caused by them are important factors to clarify the mechanism of urban fires. Nevertheless, their systematic engineering study has not been greatly implemented because of limited availability of experimental facilities. Therefore, the authors performed a Fire Wind Tunnel experiment using a real-scale fire preventive wooden house to investigate firebrands. This study is aimed at quantitatively and qualitatively elucidating the chronological relationship of fire evolution and firebrand generation.