PURPOSE: To obtain a mounting structure wherein it prevents a crosstalk noise from being generated between adjacent TAB leads, it eliminates the influence of the noise on the TAB leads or on a TAB-IC, it is excellent in a high-frequency characteristic and its cost is low by a method wherein the TAB-IC is mounted on a cavity part in a multilayer board and its upper part is covered with a subboard.

CONSTITUTION: Dielectric layers 15b to 15d whose thickness has been controlled in such a way that a conductor layer 17 for signal use has been impedance- matched are provided between the conductor layer 17 for signal use and conductor layers 16a, 16b for grounding use. A cavity part 18 which can house a TAB-IC 21 and a cutout part 19 which houses a TAB lead 9 are formed in such a multilayer board 14. An IC part 2 for the TAB-IC 21 is mounted on the cavity part 18, and the TAR-lead 9 is mounted on the cutout part 19 so as to be fitted; the TAB lead 9 is connected to the conductor layer 17 for signal use; the IC is mounted. In addition, the upper part of the TAB-IC 21 is covered with a subboard 20 provided with a conductor layer 20b for grounding use; the IC is buried and installed inside the multilayer board 14.