Heating device for preforms, capable of accurate and highly localized heating of the preforms before the blow molding step of the process of producing bottles or containers from plastic materials. This device comprises two or more heating modules (11-16), each comprising a through opening (100) in the direction of the thickness of the heating module and a heating element (5) positioned in the vicinity of the through opening. The modules (11-16) are assembled such that the through openings (100) are aligned reciprocally with each other to define a conditioning cavity for the heating device (1). Each heating module (11-16) comprises induction means (2).