To provide a method for eptaxially growing a thin film on a silicon single-crystal substrate by a vertical vapor phase epitaxial growth system, in which the auto dope quantity of the thin film can be suppressed.

An induction heating coil 6 disposed in a reaction container 2 is surrounded by a coil cover 7, and a space surrounded by the coil cover 7 is purged with a coil purge gas G. Under this state, a susceptor 5 is heated using an induction heating coil 6 and a material gas is supplied, while heating a silicon single-crystal substrate 12 mounted on the susceptor 5 to grow a thin film epitaxially in vapor phase on the silicon single-crystal substrate 12. A hole 14 is made, as a coil purge gas G outflow part, in the wall part touching the space 16 of the coil cover 7 on the rear side of the susceptor, and the gap 16 between the susceptor 5 and the coil cover 7 is purged with the coil purge gas G flowing out trough this hole 14.