EXHAUST GAS PURIFICATION APPARATUS FOR AN INTERNAL COMBUSTION ENGINE

The concentration of an additive agent supplied to a catalyst is made more uniform. Provision is made for a variable capacity type turbocharger (50) arranged in an exhaust passage (3), a catalyst (5) arranged at the downstream side of the variable capacity type turbocharger (50), and a supply device for supplying the additive agent into the exhaust passage (3) at a location upstream of the catalyst, wherein a control device is provided that adjusts, when supplying the additive agent from the supply device, the degree of opening of nozzle vanes (57) in such a manner that the speed of a swirling flow of exhaust gas generated when the exhaust gas of the internal combustion engine passes through the variable capacity type turbocharger (50) falls within a predetermined range.