A charging device comprising: an output terminal unit configured to be connected to an input terminal unit of a battery pack, wherein the output terminal unit comprises: a terminal body comprising an output terminal configured to be connected to the input terminal unit; and a terminal cover arranged to, in a first position, cover the output terminal so that the output terminal is not exposed to an outside of the output terminal unit before the input terminal unit of the battery pack is connected to the output terminal unit and configured to move to a second position in which the output terminal passes through a terminal penetration part defined in the terminal cover and protrudes to the outside of the output terminal unit while the input terminal unit of the battery pack is connected to the output terminal unit, wherein a rib penetration part through which a pressing rib of the battery pack extending from the battery pack is able to pass is defined in the terminal cover, the output terminal unit further comprises a lever coupled to the terminal cover and configured to selectively be in a hooked state with the terminal body to prevent the terminal cover from moving from the first position to the second positon, and the lever is configured to be rotated by the pressing rib passing through the rib penetration part while the input terminal unit of the battery pack is connected to the output terminal unit so that the hooked state of the lever with respect to the terminal body is released and the terminal cover can move to the second position. an output terminal unit configured to be connected to an input terminal unit of a battery pack, wherein the output terminal unit comprises: a terminal body comprising an output terminal configured to be connected to the input terminal unit; and a terminal cover arranged to, in a first position, cover the output terminal so that the output terminal is not exposed to an outside of the output terminal unit before the input terminal unit of the battery pack is connected to the output terminal unit and configured to move to a second position in which the output terminal passes through a terminal penetration part defined in the terminal cover and protrudes to the outside of the output terminal unit while the input terminal unit of the battery pack is connected to the output terminal unit, wherein a rib penetration part through which a pressing rib of the battery pack extending from the battery pack is able to pass is defined in the terminal cover, the output terminal unit further comprises a lever coupled to the terminal cover and configured to selectively be in a hooked state with the terminal body to prevent the terminal cover from moving from the first position to the second positon, and the lever is configured to be rotated by the pressing rib passing through the rib penetration part while the input terminal unit of the battery pack is connected to the output terminal unit so that the hooked state of the lever with respect to the terminal body is released and the terminal cover can move to the second position. a terminal body comprising an output terminal configured to be connected to the input terminal unit; and a terminal cover arranged to, in a first position, cover the output terminal so that the output terminal is not exposed to an outside of the output terminal unit before the input terminal unit of the battery pack is connected to the output terminal unit and configured to move to a second position in which the output terminal passes through a terminal penetration part defined in the terminal cover and protrudes to the outside of the output terminal unit while the input terminal unit of the battery pack is connected to the output terminal unit, wherein a rib penetration part through which a pressing rib of the battery pack extending from the battery pack is able to pass is defined in the terminal cover, the output terminal unit further comprises a lever coupled to the terminal cover and configured to selectively be in a hooked state with the terminal body to prevent the terminal cover from moving from the first position to the second positon, and the lever is configured to be rotated by the pressing rib passing through the rib penetration part while the input terminal unit of the battery pack is connected to the output terminal unit so that the hooked state of the lever with respect to the terminal body is released and the terminal cover can move to the second position.