To sufficiently ensure rustproofing measures for a screw thread without degrading operativity in fastening and loosening.

The tube end protector is to be mounted on a tube end threaded part of a tube 12 having a trapezoidal screw thread at an end. A groove width b of a thread 11a to be screwed with a screw 12a at the tube end threaded part of the tube 12 formed on the protector 11 is 1.1 to 2.0 times a screw thread width (a) of the screw 12a at the tube end threaded part. A height d of the thread 11a of the protector 11 is 0.5 to 1.0 time a height c of the screw 12a of the tube end threaded part. Even if a material is steel, a synthetic resin or a combination thereof, a rustproofing agent filled in a gap between threads can be effectively prevented from flowing out to well keep rustproofing performance while operativity in fastening or loosening can be kept without degradation.