A power supply of an image forming device with a heatsink fixed on a circuit board using an iron rivet is described. The rivet is fastened using a riveter. A crimped portion at a tip of the rivet, a bottom face of the heatsink, an end portion of a flange of the rivet and a land portion of the circuit board are firmly connected to each other to stabilize their electrical connection. The rivet is electrically connected to the land portion by the binding strength of the rivet and the dipped solder. Thus, the heatsink is securely connected to a grounding line of the circuit board in a simple process.