PURPOSE: To uniformly inject a pickle liquid regardless of a soft part and a hard part of a raw material mass.

CONSTITUTION: When a raw material mass is intermittently fed by a feed conveyer 2 and the raw material mass reaches prescribed position, the raw material mass is detected by a sensor 46 and a feed conveyer 2 is driven by a feed conveyer driving mechanism of AC servomotor 32 and a program controller 44 is connected to the sensor 46 and a feed conveyer driving mechanism and the feed conveyer driving mechanism is subjected to program control by a program controller 44 based on a detection signal of the sensor 46. Then, when a soft part A of the raw material mass is located at the position of injection needle 1, the feed conveyer 2 is driven with relative large feed stroke and when hard part B of raw material mass is located at the position of injection needle 1, the feed conveyer 2 is driven with relative small feed stroke.