A direct measurement of ion and neutral temperatures simultaneously in the lower ionosphere was sucessfully carried out by a shadow method from a sounding rocket launched from Uchinoura, Kagoshima, Japan, on September 22, 1973. The apparatus based on this method and the obtained data of ion and neutral temperatures together with electron density simultaneously measured by a new direct display system of the electron density and temperature are described in detail. The data are consistent with the prediction that ion and neutral temperatures are nearly equal to each other in the lower ionosphere, and they show the existence of interesting gross structures in the temperature profiles of this region.