A cover (220, 320, 420) for covering a part in a circumferential direction of an outer circumferential surface of a rigid endoscope 10 includes an outer cover portion (222, 322, 422) having flexibility and an inner cover portion (223, 323, 423) provided on an inner surface of the outer cover portion (222, 322, 422) and configured to define a flow passage for a washing fluid to be supplied to an observation window portion 14 of the rigid endoscope 10, and the outer cover portion(222, 322, 422) is mounted onto the outer circumferential surface of the rigid endoscope 10 by the outer cover portion (222, 322, 422) bending.
