Turbine of a turbocharger

A turbine is provided which can reduce variations in mass flow at throats even when the flow rate of fluid is low or high, to prevent a decrease in performance. The invention employs a turbine including a turbine rotor (80) which has turbine blades (82); a turbine housing (60) which accommodates the turbine rotor and whose cross-sectional area (A) of a scroll portion formed between the housing and the turbine rotor gradually decreases; a plurality of fixed vanes (102) which are fixed along a curved line dividing the scroll portion into an inner scroll part (66) and an outer scroll part (68); communicating parts (101) which are formed between the adjacent fixed vanes (102) and communicate between the inner scroll part and the outer scroll part; and a switch valve (90) which switches a flow path in the housing either to the inner scroll part or to both the inner scroll part and the outer scroll part; wherein a rate of change of A/R with respect to a fluid flow direction at a first position is made larger than a rate of change of A/R with respect to the fluid flow direction at a second position located at a downstream side of the first position, where A indicates a flow path area of the outer scroll part and R indicates a distance from a flow path center of the outer scroll part to a rotation center of the turbine rotor.