A holding device is a holding device that holds the medical device, and includes an arm configured to have a holder, which holds the medical device, at a distal end, a base configured to rotatably support the arm by a first joint, a disk attached to the arm, and a brake attached to the base and configured to press the disk, in which a distance between a center of rotation of the disk and a region where the brake presses the disk is changed depending on a rotation angle of the first joint.