The effects of an inner rotating plate on the heat transfer in a differentially heated inclined enclosure were investigated experimentally. The aspect ratio of the enclosure (height/width) was 1 throughout the experiments. An acrylic plate with a small thermal conductivity was installed horizontally at the center of the square enclosure, and was rotated at various speeds by using a motor attached outside of the enclosure. The inclination angle of the enclosure was varied from 90° to 90°. Purified water was used for the working fluid. The flow pattern was sketched by a visualization experiment using aluminum powder. The heat transfer enhancement can be clearly seen for the inclined enclosure with the hot wall downward facing. The rotating plate used here is useful for the regulation of a wide-ranging heat transfer rate.