PURPOSE: To dispense with a work for confirming a vacuum gauge during a resin sealing process by a method wherein, after the interior of a metal mold is sealed, the interior is evacuated for a constant time and the degree of vacuum reached at that time is compared with a set degree of vacuum to decide whether there is an abnormality or not.

CONSTITUTION: When a metal mold is brought into a state that the metal mold is clamped, a clamping detector 4 outputs a signal and a solenoid valve 2 is opened by a vacuum control means 52 to start an evacuation in the metal mold. The degree of vacuum in this metal mold is detected by a vacuum gauge 3 and the measured value is inputted in a decision means A53. The means A 53 decides whether the degree of vacuum reached a setpoint within a previously set constant time and in case the degree of vacuum reached the setpoint, a plunger 1b is driven to pour a sealing resin. In case the degree of vacuum does not reach the setpoint, a display signal is outputted to an alarm display A6 and at the same time, a signal for stopping an operation is outputted to the means 52.