A device for measuring oral cavity pressure includes the following: a pressure measuring probe 1 having a configuration in which a balloon 4 made of an elastic material is supported by a balloon base 5; a communicating member having an inner bore that communicates with the inside of the balloon via the balloon base to transmit the air pressure in the balloon; and a pressure detecting unit 8 that is connected to the rear end of the communicating member and detects the transmitted air pressure. The balloon includes a pressure receiving portion 4a that forms a cavity and a balloon tubular portion 4b that communicates with the inside of the pressure receiving portion, and the balloon is joined to the front end portion of the balloon base with the balloon tubular portion. The balloon base has a rib 5c that protrudes outward along the outer circumferential direction of the front end portion on the balloon side. The device for measuring oral cavity pressure uses the pressure measuring probe including a flat balloon and allows the balloon to be inserted into the oral cavity in an appropriate state, and thus stably can ensure good measurement accuracy.