A rail inspection device is provided. The rail inspection device includes: a drive part configured to drive on a lower rail; side wheels configured to rotate such that the drive part moves in a first direction on the lower rail, wherein the side wheels are provided on two side surfaces of the drive part opposite to each other in a second direction that intersects the first direction; upper wheels provided on an upper surface of the drive part and configured to rotate in contact with a branch guide rail provided above an upper portion of the drive part; a body connected to a lower surface of the drive part in a third direction that is perpendicular to the first direction and the second direction; and an inclination sensor provided on the upper surface of the drive part and configured to measure an inclination of the body.