At the time of performing resin molding for a matrix frame in the fabrication of semiconductor integrated circuit devices, a predetermined amount of air is fed into each of first cavities in a first row and second cavities in a second row, the first and second cavities being formed in a matrix arrangement in a lower mold of a molding die, so as to pressurize the interiors of the cavities, and a sealing resin is charged into the cavities, while the pressure therein is regulated in such a manner that the charging speeds of the sealing resin become equal in all of the cavities, whereby it is possible to stabilize the quality of the product being obtained.