To provide an injection needle disposal box for unscrewing a syringe body and a needle unit from a pen-type syringe, and making the separated needle unit fall and housing the same.

An insertion hole portion 3 for allowing a needle unit to be inserted has an inner diameter a bit smaller than the outer diameter of a needle unit 12. The needle unit 12 of a used pen-type syringe is inserted into the insertion hole portion 3, the projection streak of the needle unit 12 is engaged with the projection streak of the insertion hole section 3 in a rotation direction, and a syringe body 11 is rotated while regulating the rotation of the needle unit 12. In this way, the syringe body 11 and the needle unit 12 are unscrewed from each other. The needle unit 12 is kept to be inserted into the insertion hole portion 3, and in this state, a closing member 6 is closed. Thus, a depressing portion 6c formed on the lower surface of the same abuts on and is depressed into the needle unit 12, thereby making the needle unit 12 fall into a container body 1.