An elastic tubular body includes a grommet fitted to an opening edge of a mounting hole of a support body, a flared portion formed in a flare shape and deformable so as to invert an inner face and an outer face and having a large diameter edge coupled to the grommet; and a bellows-like tube of a bellows-like tubular shape having a smaller diameter than an inner diameter of a small diameter edge of the flared portion, a first end of the bellows-like tube connected with the small diameter edge of the flared portion. The flared portion is configured to be in a state projecting from the grommet or in a state where the outer face is reversed to enter inside the inner face and store the flared portion in a storage space of the grommet. The bellows-like tube is stored inside the flared portion stored in the storage space.