An endoscope apparatus comprising: an insertion portion extending along a longitudinal axis; a roller (61A, 61B, 61C) configured to be driven by a drive force to rotate around the longitudinal axis of the insertion portion; and a cover member configured to be attached to the insertion portion to cover the roller (61A, 61B, 61C), wherein the cover member comprises: a base layer having: an outer surface direction side; and an inner surface direction side arranged to contact the roller (61A, 61B, 61C), wherein portions of the base layer covering the roller (61A, 61B, 61C) as the roller (61A, 61B, 61C) rotates around the longitudinal axis of the insertion portion are configured to be elastically elongated in an outer surface direction of the insertion portion; and an external coating layer formed on at least one of the outer surface direction side and the inner surface direction side of the base layer, wherein the external coating layer comprises a material selected such that a coefficient of friction of an outer surface of the cover member is reduced compared to a coefficient of friction of the base layer. an insertion portion extending along a longitudinal axis; a roller (61A, 61B, 61C) configured to be driven by a drive force to rotate around the longitudinal axis of the insertion portion; and a cover member configured to be attached to the insertion portion to cover the roller (61A, 61B, 61C), wherein the cover member comprises: a base layer having: an outer surface direction side; and an inner surface direction side arranged to contact the roller (61A, 61B, 61C), wherein portions of the base layer covering the roller (61A, 61B, 61C) as the roller (61A, 61B, 61C) rotates around the longitudinal axis of the insertion portion are configured to be elastically elongated in an outer surface direction of the insertion portion; and an external coating layer formed on at least one of the outer surface direction side and the inner surface direction side of the base layer, wherein the external coating layer comprises a material selected such that a coefficient of friction of an outer surface of the cover member is reduced compared to a coefficient of friction of the base layer. a base layer having: an outer surface direction side; and an inner surface direction side arranged to contact the roller (61A, 61B, 61C), wherein portions of the base layer covering the roller (61A, 61B, 61C) as the roller (61A, 61B, 61C) rotates around the longitudinal axis of the insertion portion are configured to be elastically elongated in an outer surface direction of the insertion portion; and an outer surface direction side; and an inner surface direction side arranged to contact the roller (61A, 61B, 61C), wherein portions of the base layer covering the roller (61A, 61B, 61C) as the roller (61A, 61B, 61C) rotates around the longitudinal axis of the insertion portion are configured to be elastically elongated in an outer surface direction of the insertion portion; and an external coating layer formed on at least one of the outer surface direction side and the inner surface direction side of the base layer, wherein the external coating layer comprises a material selected such that a coefficient of friction of an outer surface of the cover member is reduced compared to a coefficient of friction of the base layer.