Provided is a vibration isolation device such that weight reduction can be achieved and it is possible to simplify the structure of a resin molding die for molding the bracket member. Engagement in a direction where the external member (60) slips out of the bracket member (30) occurs in a structure achieved in such a way that a pair of first wall section parts (62) of the external member (60) are installed inside the bracket member (30). As a result, it is possible to curb a situation where, as in the case of conventional vibration damping devices, undercut shapes are formed. Consequently, it is possible to simplify the structure of the resin molding die for molding the bracket member (30). Furthermore, as regards the external member (60), a portion between the leg sections (50), which form a pair, is omitted, and therefore, weight can be reduced correspondingly.