A high-frequency package (2, 2') comprising: a high-frequency semiconductor; a multilayer dielectric substrate having the high-frequency semiconductor mounted on a surface-layer ground conductor (53, 57); and an electromagnetic shielding member (24, 25) configured to cover a part of a surface layer of the multilayer dielectric substrate and the high-frequency semiconductor, wherein the multilayer dielectric substrate includes: a first signal via configured to be connected to a bias-and-control-signal terminal of the high-frequency semiconductor, and arranged inside the electromagnetic shielding member (24, 25); a second signal via arranged outside the electromagnetic shielding member (24, 25), and configured to be connected to an external terminal for a bias and control signal; an internal-layer signal line configured to connect between the first signal via and the second signal via; and an internal-layer ground conductor arranged around the first signal via, the second signal via, and the internal-layer signal line, characterized in that a plurality of ground vias (75, 75b, 75c, 81) is arranged around the first signal via, the second signal via, and the internal-layer signal line, on the internal-layer ground conductor, and a resistance film is provided on at least one of an upper surface and a lower surface of the internal-layer signal line so as to suppress leakage of a high-frequency component to the outside via the internal-layer signal line, and wherein the plurality of ground vias include: plural ground vias arranged around each of the first signal via and the second signal via with a dielectric material disposed between each respective signal via and the ground vias so as to shield electric fields from the signal vias; and plural RF shielding vias provided near a portion right under the electromagnetic shielding member in the first layer of the multilayer dielectric substrate so as to shield a high-frequency component generated from the high-frequency semiconductor, the RF shielding vias being disposed in a space defined between the first signal via and the second signal via. a high-frequency semiconductor; a multilayer dielectric substrate having the high-frequency semiconductor mounted on a surface-layer ground conductor (53, 57); and an electromagnetic shielding member (24, 25) configured to cover a part of a surface layer of the multilayer dielectric substrate and the high-frequency semiconductor, wherein the multilayer dielectric substrate includes: a first signal via configured to be connected to a bias-and-control-signal terminal of the high-frequency semiconductor, and arranged inside the electromagnetic shielding member (24, 25); a second signal via arranged outside the electromagnetic shielding member (24, 25), and configured to be connected to an external terminal for a bias and control signal; an internal-layer signal line configured to connect between the first signal via and the second signal via; and an internal-layer ground conductor arranged around the first signal via, the second signal via, and the internal-layer signal line, a first signal via configured to be connected to a bias-and-control-signal terminal of the high-frequency semiconductor, and arranged inside the electromagnetic shielding member (24, 25); a second signal via arranged outside the electromagnetic shielding member (24, 25), and configured to be connected to an external terminal for a bias and control signal; an internal-layer signal line configured to connect between the first signal via and the second signal via; and an internal-layer ground conductor arranged around the first signal via, the second signal via, and the internal-layer signal line, characterized in that a plurality of ground vias (75, 75b, 75c, 81) is arranged around the first signal via, the second signal via, and the internal-layer signal line, on the internal-layer ground conductor, and a resistance film is provided on at least one of an upper surface and a lower surface of the internal-layer signal line so as to suppress leakage of a high-frequency component to the outside via the internal-layer signal line, and wherein the plurality of ground vias include: plural ground vias arranged around each of the first signal via and the second signal via with a dielectric material disposed between each respective signal via and the ground vias so as to shield electric fields from the signal vias; and plural RF shielding vias provided near a portion right under the electromagnetic shielding member in the first layer of the multilayer dielectric substrate so as to shield a high-frequency component generated from the high-frequency semiconductor, the RF shielding vias being disposed in a space defined between the first signal via and the second signal via. plural ground vias arranged around each of the first signal via and the second signal via with a dielectric material disposed between each respective signal via and the ground vias so as to shield electric fields from the signal vias; and plural RF shielding vias provided near a portion right under the electromagnetic shielding member in the first layer of the multilayer dielectric substrate so as to shield a high-frequency component generated from the high-frequency semiconductor, the RF shielding vias being disposed in a space defined between the first signal via and the second signal via.