A display device comprising: a flexible display panel; a roller on which the display panel is rolled or unrolled; a housing having an opening through which the display panel passes, and providing an internal accommodation space, the roller rotatably mounted in the internal accommodation space; and a door assembly mounted in the internal accommodation space at a position adjacent to the opening of the housing, and opening and closing the opening, wherein the door assembly comprises: a door for opening and closing the opening; a motor for providing power to the door; a first shaft gear disposed between the motor and the door, and transmitting the power, provided by the motor, to the door; a first shaft having a first end connected to the first shaft gear, and rotating together with the first shaft gear; a joint connected to a second end of the first shaft; a second shaft having a first end connected to the joint, and rotating together with the first shaft; and a second shaft gear connected to a second end of the second shaft, and transmitting power to the door, characterized in that the first shaft comprises a first joint through hole formed adjacent to the second end of the first shaft in a diametral direction of the first shaft, and the joint comprises: a body which has an elongated cylindrical shape, and into which the second end of the first shaft with the first joint hole is inserted; and a first locking pin inserted into the first joint hole in a diametral direction through the body. a flexible display panel; a roller on which the display panel is rolled or unrolled; a housing having an opening through which the display panel passes, and providing an internal accommodation space, the roller rotatably mounted in the internal accommodation space; and a door assembly mounted in the internal accommodation space at a position adjacent to the opening of the housing, and opening and closing the opening, wherein the door assembly comprises: a door for opening and closing the opening; a motor for providing power to the door; a first shaft gear disposed between the motor and the door, and transmitting the power, provided by the motor, to the door; a first shaft having a first end connected to the first shaft gear, and rotating together with the first shaft gear; a joint connected to a second end of the first shaft; a second shaft having a first end connected to the joint, and rotating together with the first shaft; and a second shaft gear connected to a second end of the second shaft, and transmitting power to the door, characterized in that the first shaft comprises a first joint through hole formed adjacent to the second end of the first shaft in a diametral direction of the first shaft, and the joint comprises: a body which has an elongated cylindrical shape, and into which the second end of the first shaft with the first joint hole is inserted; and a first locking pin inserted into the first joint hole in a diametral direction through the body. a door for opening and closing the opening; a motor for providing power to the door; a first shaft gear disposed between the motor and the door, and transmitting the power, provided by the motor, to the door; a first shaft having a first end connected to the first shaft gear, and rotating together with the first shaft gear; a joint connected to a second end of the first shaft; a second shaft having a first end connected to the joint, and rotating together with the first shaft; and a second shaft gear connected to a second end of the second shaft, and transmitting power to the door, characterized in that the first shaft comprises a first joint through hole formed adjacent to the second end of the first shaft in a diametral direction of the first shaft, and the joint comprises: a body which has an elongated cylindrical shape, and into which the second end of the first shaft with the first joint hole is inserted; and a first locking pin inserted into the first joint hole in a diametral direction through the body. a body which has an elongated cylindrical shape, and into which the second end of the first shaft with the first joint hole is inserted; and a first locking pin inserted into the first joint hole in a diametral direction through the body.