The authors evaluated the electron detection performance of a diamond avalanche diode (DAD) detector. In the electrode region, the gain was uniformly about 103 with little noise. Meanwhile, an avalanche multiplication occurred locally. In the avalanche region, a total gain of 5×104 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.