Erosion at the inner walls of hollow cylinders, in which cavitating jets flowed, was investigated experimentally using the jet cavitation erosion tester. Aluminum specimens with the representative size of 20 mm length, 20 mm outer diameter, and 5 mm inner diameter were prepared. The chamfered specimens had chamfers of 0.5, 1, 3, and 5 mm; the tapered specimens had tapers of 2.9°, 5.7°, 11.5°, and 17.2°. The test fluid was hydraulic oil with a viscosity grade of 32 and the oil temperature was maintained at 40°C. The upstream and downstream absolute pressures were 10.1 and 0.2 MPa. The standoff distance from the nozzle outlet and the specimen end surface was 15 mm. The exposure time was 8 hours and they were halved and observed after the experiment. The inner walls of the chamfered specimens were partially eroded at a slightly shorter distance from the chamfered edge of the downstream side, regardless of the chamfer magnitude. The erosion of divergent tapered specimens was not confirmed under the conditions.