A plasma processing apparatus includes a worktable in a process chamber to horizontally place a target substrate thereon. A plasma generation space is defined above and around the worktable within the process chamber. The plasma generation space includes a peripheral plasma region and a main plasma region respectively located outside and inside an outer edge of the target substrate placed on the worktable. The apparatus further includes a magnetic field forming mechanism configured to form a magnetic field within the peripheral plasma region. The magnetic field includes magnetic force lines extending through the peripheral plasma region between a start position and an end position, at least one of which is located radially inside a sidewall of the process chamber.