An air conditioner comprising: a housing comprising an outlet; a panel attachable to or detachable from a lower side of the housing and comprising an inlet to introduce air therethrough; a first filter installable to the panel to filter the introduced air; a second filter installable to the panel and configured to further filter the introduced air; a lifter configured to detach the panel from the lower side of the housing by lowering the panel from an initial position, and to attach the panel to the lower side of the housing by lifting the panel from a maintenance position, wherein when the panel is lowered to the maintenance position, one or more of the first filter and the second filter are accessible for maintenance thereon, wherein the first filter and the second filter are configured to be lowered with the panel when the panel is being lowered by the lifter, and configured to be lifted with the panel when the panel is being lifted by the lifter, characterised in that the second filter is configured to filter the introduced air using an electrostatic force, the second filter is an electrostatic precipitator filter, and a power supply is disposed inside of the housing and configured to supply power to the second filter to generate the electrostatic force to filter the introduced air, wherein the second filter comprises a contact portion, wherein the power supply comprises an intermediate member (70, 80) configured to contact the contact portion electrically by being pressed by the contact portion when the panel is attached to the housing, and wherein the intermediate member (70, 80) is configured to supply power to the second filter through the contact portion when in contact with the contact portion. a housing comprising an outlet; a panel attachable to or detachable from a lower side of the housing and comprising an inlet to introduce air therethrough; a first filter installable to the panel to filter the introduced air; a second filter installable to the panel and configured to further filter the introduced air; a lifter configured to detach the panel from the lower side of the housing by lowering the panel from an initial position, and to attach the panel to the lower side of the housing by lifting the panel from a maintenance position, wherein when the panel is lowered to the maintenance position, one or more of the first filter and the second filter are accessible for maintenance thereon, wherein the first filter and the second filter are configured to be lowered with the panel when the panel is being lowered by the lifter, and configured to be lifted with the panel when the panel is being lifted by the lifter, characterised in that the second filter is configured to filter the introduced air using an electrostatic force, the second filter is an electrostatic precipitator filter, and a power supply is disposed inside of the housing and configured to supply power to the second filter to generate the electrostatic force to filter the introduced air, wherein the second filter comprises a contact portion, wherein the power supply comprises an intermediate member (70, 80) configured to contact the contact portion electrically by being pressed by the contact portion when the panel is attached to the housing, and wherein the intermediate member (70, 80) is configured to supply power to the second filter through the contact portion when in contact with the contact portion.