A process for producing a brominated 1,3-dioxolen-2-one of the following general formula (I) ##STR1## wherein R.sub.1 represents a hydrogen atom, a methyl group, or an aryl group, and R.sub.2 represents a hydrogen atom, or R.sub.1 and R.sub.2 may be bonded together to form --(CH.sub.2).sub.n -- in which n represents an integer of 3 to 5, which comprises reacting a compound of the following formula (II) ##STR2## wherein R.sub.1 and R.sub.2 are as defined, with bromine under radical generating conditions.