A method of packaging an electrical device including following steps is provided. A circuit board including a substrate and a first conductive pattern is provided. The electrical device having an electrode is disposed on the circuit board. A dielectric layer is formed on the circuit board to cover the electrical device, the electrode and the first conductive pattern, wherein a first caving pattern is foamed in the dielectric layer by the first conductive pattern. The dielectric layer is patterned to form a through hole and a second caving pattern connecting with the through hole and exposing the electrode. A conductive material is filled in the through hole and the second caving pattern to form a conductive via in the through hole and a second conductive pattern in the second caving pattern. The substrate is removed.