Injection molding machine

An injection molding machine comprising:

• a rotational driving means for driving a screw for rotation;
• a rotation amount detecting means for detecting a reverse rotation amount of the screw;
• and a resin pressure detecting means for detecting resin pressure, the injection molding machine carrying out pressure reduction control by reverse rotation of the screw,
• wherein the injection molding machine includes:
• a resin pressure gradient detecting means for detecting a gradient of resin pressure related to the reverse rotation amount of the screw in the pressure reduction control based on a reverse rotation amount detection value from the rotation amount detecting means and a pressure detection value from the resin pressure detecting means;
• and
• a pressure reduction completion determining means for determining completion of reduction of the resin pressure by comparing an absolute value of the gradient of the resin pressure detected by the resin pressure gradient detecting means with a value set in advance.