To provide a manufacturing method of forming a high quality semiconductor thin film and provide a plasma CVD apparatus achieving the manufacturing method.

A semiconductor thin film manufacturing method comprises: a process of decomposing a compound containing group 4 element atoms and hydrogen atoms into plasma and active species; and a process of depositing the active species on a substrate. In the decomposing process, plasma generation energy is intermittently supplied such that an idle period and a supply period is repeated, and the plasma generation energy temporarily varies in the supply period.