An electron beam sterilization method is provided to sterilize a bottle cap by dropping the bottle cap sequentially along a sterilization path in the vertical direction while the bottle cap is oriented such that the cap axis thereof passing through the center of an opening face is substantially horizontal, and applying an electron beam onto the bottle cap. First, in the sterilization path, an ambient gas is sucked through a suction hole formed along the vertical direction in a guide wall, thereby drawing the closed face of the bottle cap toward the guide wall, and an electron beam is applied onto the opening face. Next, in the sterilization path, an ambient gas is sucked through a suction hole formed along the vertical direction in a guide wall, thereby drawing the opening face of the bottle cap toward the guide wall, and an electron beam is applied onto the closed face.
