An interface device in accordance with the present claimed invention is an interface device 4 that intervenes between a measuring means 2 that measures brain activities of a subject H and an object 31 to be controlled, and that comprises a reference signal storing part D1 that stores a brain activity signal measured at a time when the subject H conducts predetermined thinking different from direct thinking in order to control the object 31 to be controlled in a desired mode as a reference signal, a discriminating part 41 that compares the brain activity signal measured by the measuring means 2 with the reference signal and discriminates whether or not the thinking of the subject H is the predetermined thinking, and a controlling part 42 that controls the object 31 to be controlled in the desired mode when the discriminating part 41 discriminates that the thinking of the subject H is the predetermined thinking.