This study investigated convective heat transfer inside a rotating two-pass rectangular channel with guide vanes in the turning region. The objective was to determine the effect of the guide vanes on blade tip cooling. The channel had a hydraulic diameter of 26.67 mm and an aspect ratio of 5, and various guide vane configurations were used in the turning region. The Reynolds number, based on the hydraulic diameter, was held constant at 10,000 while the rotation number was 0.1. The detailed local heat transfer coefficients were determined through naphthalene sublimation using the heat and mass transfer analogy. The heat transfer was high on the trailing surface in the first-pass section and on the leading surface in the secondpass section. The heat transfer on leading and trailing surfaces increased in the rotating channel, but the heat transfer on the tip surface decreased. The peak heat transfer on the tip surface appeared in the middle of the first-pass corner due to the centrifugal force.