Abstract: A melt filling pressure difference control method controls a pressure difference used to supply melt from a holding furnace to a cavity of a casting machine by generating a pressure difference between an interior space of holding furnace and the cavity formed inside the mold. The method includes the steps of setting up a program pattern comprising time-varying characteristics of pressure difference target values, controlling the pressure difference so as to follow the program pattern that was set up, detecting whether the melt surface has risen to a predetermined level inside the cavity, compensating the program pattern based on the melt surface level when the melt surface has risen to a predetermined level inside cavity, and controlling the pressure difference between space inside the holding furnace and the cavity so as to follow the compensated program pattern.