Disclosed in an intake pipe pressure detecting device for detecting the pressure in that section of an intake pipe in an internal combustion engine which is on the downstream side of a throttle valve provided in the intake manifold. The pressure detecting device comprises a mixing chamber which has an opening in the wall of the intake pipe, a pressure introducing path which opens onto this mixing chamber, and air inlets adapted to allow fresh air to enter the mixing chamber, thereby generating an air flow directed from the mixing chamber to the intake pipe.