To provide an electron detector capable of detecting an electron at high sensitivity with no mixing of noise even when accelerating voltage of primary electron beam is low.

The electron accelerated and incident to a semiconductor detector 11 reaches a sensitive layer of the detector and generates an electric charge carrier in proportion to energy of the incident electron, and a signal electric current Is flows. The signal electric current Is inputs to an electric current voltage converter 17 and generates output voltage. The output voltage is converted to a digital data correlated to the input voltage in an AD converter 18. The digital data from the AD converter 18 is transmitted to a receiver 23 in a low voltage part 22 after bias voltage which is a direct current component is cancelled by a coupled circuit 21. The digital data received by the receiver 23 is supplied to a DA converter 25, and the output signal of the DA converter 25 is supplied to a picture image display part 26 including a cathode ray tube, etc.