The purpose of this study was to investigate the fluid flow characteristics of heat storage in sensible heat storage system for use In cooling and heating of buildings. Heat storage material was gravels and experiments were performed in the condition of constant temperature. The experimental parameters were fluid velocity and size of gravels. The experimental results of the heat storage quantity and the heat storage efficiency by the variation of packing size and fluid velocity were as the follows : The maximum value of the heat storage capacity and heat storage efficiency and the minimum arriving time for maximum heat storage were observed when the packing ratio was 72.5% and the fluid velocity was 0.14m/s.