A controller for a variable geometry type turbocharger controls a sectional area of an throttle throat of a turbine through which exhaust gases from an engine is supplied to the turbine on the basis of a engine speed and an amount of air introduced into the engine and includes a bypass path which bypasses the turbine to reduce the exhaust gases supplied to the turbine by controlling the opening and closing of the bypass path on the basis of the engine speed and the amount of air introduced into the engine, thereby preventing the degradation of the supercharged air supplied to the engine and improving torque of the engine in all the operating area of the engine.