An endoscope cover fixing device, having an open state and a closed state, and comprising: - a fixing device main body, having a concave surface with a first region and with a second region opposing the first region, and comprising: - a bent section that is deformable in a direction in which a bend amount thereof increases, whereupon the endoscope cover fixing device moves from its open state towards its closed state; and - an insert portion (54, 57): - into which an endoscope, having a longitudinal direction and covered by a sheath-like cover, is insertable; characterised in that: - the fixing device main body further comprises: - a first fixing protrusion portion protruding from the first region and comprising a first contact surface; and - a second fixing protrusion portion protruding from the second region and comprising a second contact surface; - the first fixing protrusion portion: - extends in a direction opposing a direction of protrusion of the second fixing protrusion portion; and - is arranged in a position that does not lie on a same plane as the second fixing protrusion portion; - the first contact surface and the second contact surface are disposed: - in a parallel positional relationship with a distance therebetween, which distance is the same in both the open state and the closed state; and - in a parallel positional relationship to the longitudinal direction of the covered, insertable endoscope (31, 22), were such a covered, insertable endoscope (31, 22) to be inserted into said insert portion (54, 57); whereby, when the endoscope cover fixing device moves from its open state towards its closed state first and second contact surfaces (61a, 62a) move in parallel in opposing directions such that in the closed state, a contact region of the first contact surface contacts with a position on an outer circumferential surface of the inserted, covered endoscope (31, 22) opposing a position on the outer circumferential surface that is contacted by a contact region of the second contact surface. - a fixing device main body, having a concave surface with a first region and with a second region opposing the first region, and comprising: - a bent section that is deformable in a direction in which a bend amount thereof increases, whereupon the endoscope cover fixing device moves from its open state towards its closed state; and - an insert portion (54, 57): - into which an endoscope, having a longitudinal direction and covered by a sheath-like cover, is insertable; characterised in that: - the fixing device main body further comprises: - a first fixing protrusion portion protruding from the first region and comprising a first contact surface; and - a second fixing protrusion portion protruding from the second region and comprising a second contact surface; - the first fixing protrusion portion: - extends in a direction opposing a direction of protrusion of the second fixing protrusion portion; and - is arranged in a position that does not lie on a same plane as the second fixing protrusion portion; - the first contact surface and the second contact surface are disposed: - in a parallel positional relationship with a distance therebetween, which distance is the same in both the open state and the closed state; and - in a parallel positional relationship to the longitudinal direction of the covered, insertable endoscope (31, 22), were such a covered, insertable endoscope (31, 22) to be inserted into said insert portion (54, 57); - a bent section that is deformable in a direction in which a bend amount thereof increases, whereupon the endoscope cover fixing device moves from its open state towards its closed state; and - an insert portion (54, 57): - into which an endoscope, having a longitudinal direction and covered by a sheath-like cover, is insertable; characterised in that: - into which an endoscope, having a longitudinal direction and covered by a sheath-like cover, is insertable; - the fixing device main body further comprises: - a first fixing protrusion portion protruding from the first region and comprising a first contact surface; and - a second fixing protrusion portion protruding from the second region and comprising a second contact surface; - a first fixing protrusion portion protruding from the first region and comprising a first contact surface; and - a second fixing protrusion portion protruding from the second region and comprising a second contact surface; - the first fixing protrusion portion: - extends in a direction opposing a direction of protrusion of the second fixing protrusion portion; and - is arranged in a position that does not lie on a same plane as the second fixing protrusion portion; - extends in a direction opposing a direction of protrusion of the second fixing protrusion portion; and - is arranged in a position that does not lie on a same plane as the second fixing protrusion portion; - the first contact surface and the second contact surface are disposed: - in a parallel positional relationship with a distance therebetween, which distance is the same in both the open state and the closed state; and - in a parallel positional relationship to the longitudinal direction of the covered, insertable endoscope (31, 22), were such a covered, insertable endoscope (31, 22) to be inserted into said insert portion (54, 57); - in a parallel positional relationship with a distance therebetween, which distance is the same in both the open state and the closed state; and - in a parallel positional relationship to the longitudinal direction of the covered, insertable endoscope (31, 22), were such a covered, insertable endoscope (31, 22) to be inserted into said insert portion (54, 57);