The labor involved in cleaning for each examination is reduced, the examination can be carried out hygienically, and the convenience of use is improved. An electrode apparatus for detecting brain waves which is arranged in contact with the scalp and which detects brain wave signals is provided. The electrode apparatus for detecting brain waves comprises a rod-shaped electrode apparatus main body having an electrode disposed at the tip thereof, a cap which is mountable on the tip of the electrode apparatus main body and which has an elastic member which contains an electrolyte and which is disposed making close contact so as to cover the electrode, and a connection means which detachably connects the cap to the electrode apparatus main body.