In a method of manufacturing a module board, an electronic component is mounted on a first principal surface of a small board. A cavity defining a through hole is formed in a core board. The electronic component is housed in the cavity by mounting the small board on a surface electrode arranged around the cavity. Resin layers are formed on both principal surfaces of the core board, and resin flows through a gap between the core board and the small board. Hence, the inside of the cavity is filled with the resin, and the electronic component is sealed with the resin.