To provide a method for removing a needle unit, which can safely remove the needle unit from a pen-shaped syringe without using an exclusive tool, and to provide a medical waste container.

The method includes the step of inserting a small diameter region 21 into a needle case 20 which can store a needle unit 27 in a concave removal section 17 made in a medical waste container 1 and of arranging the needle case 20 at an upright position in the concave removal part 17 with the opening 23 of the needle case 20 facing up; the step of pushing the pen-shaped syringe into the needle case 20 to engage a needle housing 26 of the needle unit 27; and the step of removing the needle unit 27 as the pen-shaped syringe is pulled upward, while keeping the needle unit 27 to be engaged to the needle case 20; and the step of putting the needle unit 27 together with the needle case 20 into the medical waste container 1 after the removal for disposal.