A device for measuring a secondary electron emission coefficient comprises a scanning electron microscope, a first collecting plate, a second collecting plate, a first galvanometer, a second galvanometer, a voltmeter, and a Faraday cup. The scanning electron microscope comprises an electron emitter and a chamber. A sample is located between the first collecting plate and the second collecting plate. The first galvanometer is used to test a current intensity of electrons escaping from the sample and hitting the first collecting plate and the second collecting plate. A high-energy electron beam emitted by the electron emitter passes through the first collecting plate and the second collecting plate, and enters the Faraday cup. The second galvanometer is used to test a current intensity of electrons entering the Faraday cup.