PURPOSE: To obtain a driving device which can be miniaturized by airtightly providing a body which expands and drives a mobile part by pressing when the body is heated by energizing a coil in part of the internal hole of a cylindri cal body between one end of the hole and the mobile part.

CONSTITUTION: A driving device is provided with a driving section 1 equipped with a coil 11a wound around a cylindrical body 11 and a mobile part 2 which is driven in the axial direction in the internal hole 11b of the cylindrical body 11 when the coil 11a is energized. In such a driving device, an expanding body 3 which expands and drives the mobile part 2 by pressing when the body 3 is heated by energizing the coil 11a is airtightly provided in part of the hole 11b between one end 11d of the hole 11b and the mobile part 2. For example, the coil 11a composed of such a high-resistance conductor as the nichrome wire is wound around the cylindrical body 11 and such a liquid as the Freon(R), ethanol, etc., having a high coefficient of expansion is used as the expanding body 3. In addition, a forcing member 23 which is formed by bending a plate spring so that the member 23 can have an inverting property and both ends of which are fixed to an external pedestal is provided.