To provide a secondary electron emission rate measuring device capable of easily measuring the secondary electron emission rate of a film to be measured at a state close to the discharge phenomenon of a plasma display panel.

The direct current discharge of rare gas is generated by applying direct current charged particle generating voltage between a pair of charged particle generating electrodes 11a, 11b. Rare gas particles which are generated by the discharge phenomenon and exist in the charge state, that is, charged particles are accelerated in direct current electric field formed between a pair of charged particle acceleration electrodes 14, 15, and a sample 1 in a sample chamber 20 is irradiated with the rare gas particles. The secondary electron emitted from a protecting layer 5 of the sample 1 is captured by a collecting electrode 22, and the secondary electron emission rate is measured by the current flowing in the collecting electrode 22 and an electrode 3.