PURPOSE: To obtain the press controller of high quality by providing a box body which has an air chamber linked with a blow-in hole, an elastic body whose reflecting surface is displaced by variation in the pressure in the air chamber, and a light emitting and a light receiving element.

CONSTITUTION: When a breath is blown from the blow-in hole 13a, the pressure in the air chamber 11 varies with the breath pressure and the elastic body 40 is displaced, so the distance from the light emitting element 50a to the light receiving element through the reflecting surface 45a varies. Consequently, the quantity of light reception of the light receiving element varies with the breath pressure and a signal corresponding to the breath pressure is outputted. Consequently, there is not any influence of an external magnetic field and the light emitting and receiving elements are put in a sealed case to remove the influence of external light and prevent misdetection originating from external conditions, thereby detecting the breath pressure with high accuracy.