The invention provides a space charge density measurement device based on a Faraday cage method. The space charge density measurement device comprises a Faraday cage body, a potential probe, a signal transmission shielded wire, a signal transmission shielded tube, a potential measurement module and a pedestal. The potential probe is positioned at the center of the Faraday cage body. The signal transmission shielded wire is positioned in the signal transmission shielded tube. The signal transmission shielded tube is supported between the bottom part of the Faraday cage body and the potential probe. The potential measurement module is positioned below the Faraday cage body and is connected with the pedestal. The induction type potential probe is adopted for measuring the space potential and is high in measurement precision. The Faraday cage body shields influences of an external electric filed, the space potential in a cage is obtained, and the space charge density is further obtained. The space charge density measurement device is good in stability, and can be well applied to complex and changeable environments.