To provide the high frequency amplifier contributing to the reduction in a board occupancy area and then miniaturization by using a multilayer board.

At least one transistor(TR) 10(19) is placed on a front (rear) side of a multilayer board, and a plurality of inner layers 3, 4, 5 of the multilayer board are formed as patterns as thin film layers to configure resistive elements, inductive elements or capacitive elements. Then an inter-stage matching circuit interposed between the TR 10 on the front side and the TR 19 on the rear side is configured by a plurality of the inner layers 3, 4, 5 of the multilayer board and via-holes 15 to 18 connecting the front side conductor layer 1, the rear side conductor layer 2 and the inner layers 3, 4, 5.