To provide a ladder device for a vessel capable of accommodating a drive mechanism for raising a ladder body mounted to be raised on a hull side in a main body.

This ladder device 10 for a vessel has a main body 11 as a ladder and a drive mechanism. The main body 11 is shaped like a box, is supported by a hull, and can take a standing position and a inclined position. The drive mechanism raises and falls the main body 11 between the standing position and the inclined position. The drive mechanism is accommodated inside the main body. Therefore, no space is required for installing the drive mechanism on the hull side.