A vertical plasma processing apparatus for a semiconductor process includes a process container having a process field configured to accommodate a plurality of target substrates at intervals in a vertical direction, and a marginal space out of the process field. In processing the target substrates, a control section simultaneously performs supply of a process gas to the process field from a process gas supply circuit and supply of a blocking gas to the marginal space from a blocking gas supply circuit to inhibit the process gas from flowing into the marginal space.