This study proposes long-range nondestructive inspection of the inner surface of a pipe without open end using microwave emitted by a probe attached to the pipe wall. Three-dimensional finite element simulations were conducted to evaluate how to propagate microwave effectively inside a pipe having an inner diameter of 19 mm. The simulations considered a coaxial cable penetrating the pipe wall to emit microwave inside the pipe. Experimental verifications were then carried out using a brass pipe with a total length of 4.5 m and a probe fabricated on the basis of the results of the numerical simulations. The experiment confirmed clear reflections due to artificial wall thinning 1 m away from the probe situated approximately at the center of the pipe. The experiment also revealed that directivity of the microwave depended on the frequency, which agrees with the results of the numerical simulations.