The present invention herein provides ceramic powder which is to be incorporated into rubber or a resin and which can be used as, for instance, a semiconductor-sealing material and for the preparation of a composition excellent in the narrow interstice-filling up property and moldability. The ceramic powder has a multiple peak-frequency type particle size distribution which has at least two peaks, as determined according to the laser diffraction-scattering type particle size distribution analyzer, wherein the maximum particle size observed for the first peak falls within the range of from 12 to 30 μm; that observed for the second peak falls within the range of from 2 to 7 μm; the content of the particles having a particle size of greater than 7 μm and less than 12 μm is not more than 18% (including 0%); and wherein the ratio (F2/F1) of the frequency value F2 of the maximum particle size for the second peak to that F1 of the maximum particle size for the first peak ranges from 0.5 to 1.3.