The present invention aims to provide a gasket which reduces the clamping force required to fit a plunger rod into the gasket, while maintaining a tight fit therebetween. The present invention relates to a medical gasket including a female screw portion to fit a plunger, on the side opposite to a drug contact surface, the female screw portion having roots or crests which gradually increase in diameter from the drug contact surface side toward the opposite plunger side.
