We report on the effect of the beveled mesa angle on the performance of 4H-SiC avalanche photodiodes (APDs) with various active areas between 100 and 500 mu m. The mesa structure was beveled with a smaller slope angle by using a photoresist reflow technique to suppress edge breakdown. Some beveled mesa APDs with a small angle of 10.5 degrees were studied using high-resolution transmission electron microscopy and an electrical and optical measurement system compared with APDs with large slope angles of 28.5 degrees. The study results show that a small-slope beveled mesa APD shows more uniform dark current level in the linear region, regardless of the active area with a sharp breakdown, and a lower dark count rate than the larger slope-angle APD.