A method for producing porous silica-based particles having an average particle diameter of 0.5 to 30 μm, which comprises the steps of: (a) spray-drying a dispersion of fine silica-based particles, or a mixture of the above dispersion of the fine silica-based particles and an aqueous solution of silicic acid with use of a spray dryer, said fine silica-based particles having an average particle diameter which is not more than 0.5 μm, to obtain a dried powder of porous silica-based particles having diameters ranging primarily from 0.1 to 50 μm; (b) putting the dried powder of the porous silica-based particles obtained in the step (a) into water and then stirring a slurry of the mixture under pH conditions on which the zeta potential of the porous silica-based particles contained in the water comes to in a range of -15 to -70 mV, to obtain a dispersion of porous silica-based particles with a foreign matter attached to the surface thereof having been removed therefrom; (c) subjecting the dispersion obtained in the step (b) to a wet classification device at which a supernatant containing at least porous silica-based particles having diameters of less than 0.5 μm is separated and removed, to obtain a dispersion containing porous silica-based particles having diameters ranging primarily from 0.5 to 50 μm; (d) subjecting the dispersion obtained in the step (c) to a wet classification device at which a sediment or precipitates containing at least porous silica-based particles having diameters of more than 30 μm is separated and removed, to obtain a dispersion containing porous silica-based particles having diameters ranging primarily from 0.5 to 30 μm; (e) filtering the dispersion obtained in the step (d) to separate solid materials contained therein, to obtain a cake-like substance of porous silica-based particles; and (f) drying the cake-like substance obtained in the step (e) and then crushing or breaking up a group of thus obtained particles, to obtain a dried powder of porous silica-based particles having an average particle diameter of 0.5 to 30 μm. (a) spray-drying a dispersion of fine silica-based particles, or a mixture of the above dispersion of the fine silica-based particles and an aqueous solution of silicic acid with use of a spray dryer, said fine silica-based particles having an average particle diameter which is not more than 0.5 μm, to obtain a dried powder of porous silica-based particles having diameters ranging primarily from 0.1 to 50 μm; (b) putting the dried powder of the porous silica-based particles obtained in the step (a) into water and then stirring a slurry of the mixture under pH conditions on which the zeta potential of the porous silica-based particles contained in the water comes to in a range of -15 to -70 mV, to obtain a dispersion of porous silica-based particles with a foreign matter attached to the surface thereof having been removed therefrom; (c) subjecting the dispersion obtained in the step (b) to a wet classification device at which a supernatant containing at least porous silica-based particles having diameters of less than 0.5 μm is separated and removed, to obtain a dispersion containing porous silica-based particles having diameters ranging primarily from 0.5 to 50 μm; (d) subjecting the dispersion obtained in the step (c) to a wet classification device at which a sediment or precipitates containing at least porous silica-based particles having diameters of more than 30 μm is separated and removed, to obtain a dispersion containing porous silica-based particles having diameters ranging primarily from 0.5 to 30 μm; (e) filtering the dispersion obtained in the step (d) to separate solid materials contained therein, to obtain a cake-like substance of porous silica-based particles; and (f) drying the cake-like substance obtained in the step (e) and then crushing or breaking up a group of thus obtained particles, to obtain a dried powder of porous silica-based particles having an average particle diameter of 0.5 to 30 μm.