A dust collector for collecting dust, in which the rarefaction of a dielectric at the rear part of electric field forming apparatus is prevented, whereby the collecting efficiency can be increased. The dust collector includes a charging device for charging a substance to be collected, such as dust and mist, contained in a gas; a sprayer device for spraying a dielectric on the substance to be collected which is charged by the charging device; an electric field forming device, having first and second electrodes and which form a direct current electric field and dielectrically polarize the dielectric sprayed by the spray device; and a dielectric collecting device for collecting the dielectric which has arrested the substance to be collected. The spray device includes grounding device and for electrically grounding the dielectric before being sprayed to let a charge of the dielectric escape.