Shrink-fitting device for clamping and unclamping tools that have a tool shank, having a tool receptacle which has a sleeve part that is open at its free end and is made of electrically conductive material, for receiving the tool shank in a frictional manner, and having an induction coil that encloses the sleeve part of the tool receptacle, is able to be subjected to a high-frequency alternating current and is configured as a ring coil or a cylindrical coil, for heating the sleeve part, wherein the induction coil bears, on its outer circumference, a first casing made of magnetically conductive and electrically non-conductive material, and the device comprises power semiconductor components for producing an alternating current feeding the induction coil, and an induction coil housing that preferably consists of insulating material, wherein the induction coil and its first casing are surrounded at the outer circumference by a second casing which consists of magnetically non-conductive material and electrically conductive material and is designed such that a stray field that occurs in the vicinity thereof generates eddy currents in the second casing and as a result the stray field is weakened, and in that at least the power semiconductor components are accommodated together with the induction coil in an induction coil housing which encloses the induction coil, the first and second casing thereof, and the power semiconductor components, at least around the circumference of the induction coil.