PURPOSE: To reduce the difference between the actual injecting speed and a setting injecting speed, to execute the operation meeting the actual condition in short period and to quickly produce a cast product having stable quality by changing the opening degree of an injection valve based on correlation between the corrected injecting speed and the opening degree of the injection valve.

CONSTITUTION: The injecting speed measured by an injecting speed measuring instrument 21 is stored in a storing unit 22. When the measurements by an arithmetic unit 24 reach the prescribed times, the average injecting speed is calculated. Further, the difference between the setting injecting speed preset in a data setting unit 23 and the average injecting speed is calculated by the arithmetic unit 24. Thereafter, this difference is multiplied by a correcting factor prestored in the data setting device by the arithmetic unit 24, and the correcting quantity of the injecting speed curve is calculated to shift each correcting curve. By using this shifted injecting speed curve, a new opening degree of the injection valve to the setting injecting speed is calculated by the arithmetic unit 24. By using an injection valve driving device 25 and an injection valve opening degree detecting instrument 27, the injection valve 26 is automatically adjusted.