The ERG (Exploration of energization and Radiation in Geospace) project is a mission to study acceleration and loss mechanisms of relativistic electrons around the Earth. To achieve comprehensive observations of plasma/particles, fields, and waves, the Plasma Wave Experiment (PWE) is installed onboard the ERG satellite to measure electric field in the frequency range from DC to 10 MHz, and magnetic field in the frequency range from a few Hz to 100 kHz. Two CPU boards, one for electric field and another for magnetic field, are installed for the PWE and a variety of operational modes can be implemented. In the present paper, we introduce unique specifications of the PWE to meet the scientific objects of the ERG mission.