PURPOSE: To decree the pressure in a turbine rotor inlet so as to improve supercharge performance with a simple structure for a waste gate.

CONSTITUTION: A turbocharger is provided with scroll chamber 17 installed at the flange part 16 of a turbine housing 10 for communicating with a bypass passage 22, a nozzle part 19 for communicating the scroll chamber 17 with an exhaust outlet pipe 18, and formed on outer circumferential part of the exhaust outlet 14 by means of the flange part 16 and an exhaust outlet pipe 18 cross area of the scroll chamber 17 gradually decreases as approaching closer to the exhaust outlet 14.