A fine porous ammonium perchlorate (FPAP) was prepared by the spray-drying method. The burning behavior of a propellant containing FPAP was investigated and compared with that of a propellant containing a fine ammonium perchlorate without porosity (FAP), of which the mean diameter was almost the same as that of FPAP. The results are as follows: (1) The burning rate of the propellant containing FPAP increases with increasing FPAP content. (2) When the propellants containing FPAP or FAP have the same composition, the burning rate of the propellant containing FPAP is larger than that of the propellant containing FAP at various pressures. (3) The temperature sensitivity of a propellant containing FAP is relatively constant at various pressures. However the temperature sensitivity of the propellant containing FPAP decreases with increasing pressure. (4) It was found that the differences in the burning behavior of the propellant containing FPAP and the propellant containing FAP are caused by the porosity of FPAP.