A power adapter including a first substrate, a second substrate, a transformer and an insulating frame is provided. The first substrate includes a first terminal set. The second substrate includes a second terminal set. The transformer includes a primary side connection terminal and a secondary side connection terminal, wherein the primary side connection terminal is connected to the first terminal set and the secondary side connection terminal is connected to the second terminal set. The insulating frame is disposed between the first substrate and the second substrate, and the transformer leans against the insulating frame.