The authors evaluated the electron detection performance of a diamond avalanche diode (DAD) detector. In the electrode region, the gain was uniformly about 10(3) with little noise. Meanwhile, an avalanche multiplication occurred locally. In the avalanche region, a total gain of 5 x 10(4) was obtained. In some regions where the electric field is regarded to be intensified, the avalanche multiplication gain was estimated to be approximately 100-300, and the signal-to-noise ratio (S/N) was nearly equal to 1. The DAD can be applied to an electron detector for a scanning electron microscope due to its high gain and small dark current. However, it is necessary to improve the S/N and homogenize the gain to use the DAD detector as an electron detector. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3497031]