A high-frequency device manufacturing method is provided. The method includes providing a substrate; forming a conductive material on the substrate; standing the substrate and the conductive material for a first time duration; forming a conductive layer by sequentially repeating the steps of forming the conductive material and standing at least once; and patterning the conductive layer. The thickness of the conductive layer is in a range from 0.9 μm to 10 μm. A high-frequency device is also provided.