A new variable scroll type turbocharger has been developed, which is a kind of variable geometry turbocharger. This paper describes a method for determining the shape of a scroll chamber of a turbine housing of the turbocharger. The basic idea is to vary the flow area using the scroll according to exhaust gas flow. The scroll consists of several scroll pieces joined to form a linked variable structure. The shape of the scroll pieces is decided on the basis of an Archimedes’ curve. The device developed is relatively simple.