The fluid drive unit includes a cylinder communicating with both end portions of a meandering passage formed in the heat transport device. In the cylinder, the piston is slidably arranged being capable of sliding in the axial direction. Fluid is charged in the spaces, which are provided on both sides of the piston, connected to the meandering passage. The solenoid coil, which is provided in the periphery of the side of the cylinder, periodically inverts the magnetic poles and reciprocates the piston in the cylinder. To drive the piston smoothly and reduce the amount of eccentricity, a pair of sliding members are provided at the end portions of the piston. When the fluid in the passage is vibrated by the movement of the piston, the apparent heat conductivity of the heat transport device is enhanced, and heat is quickly diffused from the heating body to the radiating portion.