In this paper, we show how the finite formulation of quantum field theory based on Callan-Symanzik equations can be generalized to the case of nonrenormalizable theories. We derive an equation for effective action for an arbitrary single scalar field theory, allowing us to perform computations without running in intermediate divergencies. We illustrate the method with the use of lambda phi 4 & thorn; phi 6 /M 2 theory by the explicit (and fully finite) calculations of the effective potential as well as two-, four- and six-point correlation functions at one-loop level and demonstrate that no quantum corrections to scalar mass m 2 , depending on M 2 scale, are generated.