A ceiling mounted air conditioner comprising: a main body configured to be fixed onto a ceiling and have an open bottom; an outlet panel configured to be coupled to a lower part of the main body and have a plurality of air outlets; an intake panel configured to be coupled to the outlet panel and have an air intake; a door panel configured to be lifted up or down from the bottom of the intake panel and thus to open or shut the air intake; and a human body sensor module configured to be installed in the door panel, to begin to operate when the door panel is lifted down and to sense a movement of a user, wherein the door panel shuts the air intake when placed in contact with the bottom of the intake panel and opens the air intake when detached from the bottom of the intake panel, wherein the door panel includes an installation hole through which the human body sensor module is installed in the door panel, wherein the human body sensor module includes a sensor case which is disposed over the installation hole, protrudes beyond the installation hole and covers the installation hole, a printed circuit board, PCB, rotator which is disposed in the sensor case so as to be able to rotate and has a PCB installed thereon, a PCB driving motor which rotates the PCB rotator, and a human body sensor which is installed on the PCB, wherein the human body sensor module further includes a stopper which prevents an excessive rotation of the PCB rotator, wherein the stopper includes a protrusion which rotates along with the PCB rotator and protrudes from a connector portion or a PCB installation portion toward the sensor case, and a latch which is formed in the sensor case so as to interfere in the protrusion. a main body configured to be fixed onto a ceiling and have an open bottom; an outlet panel configured to be coupled to a lower part of the main body and have a plurality of air outlets; an intake panel configured to be coupled to the outlet panel and have an air intake; a door panel configured to be lifted up or down from the bottom of the intake panel and thus to open or shut the air intake; and a human body sensor module configured to be installed in the door panel, to begin to operate when the door panel is lifted down and to sense a movement of a user, wherein the door panel shuts the air intake when placed in contact with the bottom of the intake panel and opens the air intake when detached from the bottom of the intake panel, wherein the door panel includes an installation hole through which the human body sensor module is installed in the door panel, wherein the human body sensor module includes a sensor case which is disposed over the installation hole, protrudes beyond the installation hole and covers the installation hole, a printed circuit board, PCB, rotator which is disposed in the sensor case so as to be able to rotate and has a PCB installed thereon, a PCB driving motor which rotates the PCB rotator, and a human body sensor which is installed on the PCB, wherein the human body sensor module further includes a stopper which prevents an excessive rotation of the PCB rotator, wherein the stopper includes a protrusion which rotates along with the PCB rotator and protrudes from a connector portion or a PCB installation portion toward the sensor case, and a latch which is formed in the sensor case so as to interfere in the protrusion.