The invention relates to an electronic device and a high-frequency circuit board thereof. The high-frequency circuit board comprises a first dielectric layer, a first signal line arranged on the first dielectric layer, a second dielectric layer which is arranged on the first dielectric layer and covers the first signal line and a first electromagnetic protection layer positioned on the second dielectric layer, wherein the first electromagnetic protection layer comprises a clearance; and the position of the clearance corresponds to the position of the first signal line.