A particle of a few micrometers in diameter with a high electrostatic charge is strongly vibrated to induce a secondary flow around the particle. The flow blows the submicron particles into a region close to the charged particle, where the electrostatic gradient force becomes strong enough to adsorb the submicron particles on to the charged particle. The experimental results show that the agglomeration rate is greatly enhanced by the complementary use of the electrostatic and the hydrodynamic effects. In this paper, a fundamental consideration on the electrostatic agglomeration is also presented in combination with the concept of agglomeration volume in the acoustic agglomeration.