A film forming device (1, 2, 3, 4, 5) adapted to form a thin film on a substrate by sputtering a target, the film forming device comprising: a film formation chamber that is capable of introducing or discharging film forming gas; a target holding portion adapted to hold the target disposed in the film formation chamber; a substrate holding portion that is disposed to face the target holding portion in the film formation chamber and is adapted to hold a substrate; a radio frequency sputtering power supply adapted to generate plasma in a space between the target holding portion and the substrate holding portion, wherein an adhesion preventing mechanism adapted to prevent a target material from adhering to an inner wall surface of the film formation chamber, the target material being sputtered and scattered from the target in the film formation chamber, wherein the adhesion preventing mechanism is configured with a plurality of adhesion preventing plates including at least a substrate edge adhesion preventing plate that is provided on an edge of a region on the substrate holding portion where the substrate is provided and a substrate outer peripheral region adhesion preventing plate that is disposed on an outer periphery of the substrate edge adhesion preventing plate to be spaced from the substrate edge adhesion preventing plate, and a potential adjusting mechanism that is electrically connected to any one of the substrate edge adhesion preventing plate or the substrate outer peripheral region adhesion preventing plate and is adapted to adjust a potential of the adhesion preventing plate, wherein the adhesion preventing plate connected to the potential adjusting mechanism and an adhesion preventing plate adjacent to the adhesion preventing plate connected to the potential adjusting mechanism among the plurality of adhesion preventing plate are disposed at an interval of 0.5 mm to 3.0 mm, and characterized in that the radio frequency sputtering power supply and / or the potential adjusting mechanism are configured to decrease the plasma density stepwise, in a case where the radio frequency sputtering power supply is turned off after the piezoelectric film reaches a predetermined thickness. a film formation chamber that is capable of introducing or discharging film forming gas; a target holding portion adapted to hold the target disposed in the film formation chamber; a substrate holding portion that is disposed to face the target holding portion in the film formation chamber and is adapted to hold a substrate; a radio frequency sputtering power supply adapted to generate plasma in a space between the target holding portion and the substrate holding portion, wherein an adhesion preventing mechanism adapted to prevent a target material from adhering to an inner wall surface of the film formation chamber, the target material being sputtered and scattered from the target in the film formation chamber, wherein the adhesion preventing mechanism is configured with a plurality of adhesion preventing plates including at least a substrate edge adhesion preventing plate that is provided on an edge of a region on the substrate holding portion where the substrate is provided and a substrate outer peripheral region adhesion preventing plate that is disposed on an outer periphery of the substrate edge adhesion preventing plate to be spaced from the substrate edge adhesion preventing plate, and a potential adjusting mechanism that is electrically connected to any one of the substrate edge adhesion preventing plate or the substrate outer peripheral region adhesion preventing plate and is adapted to adjust a potential of the adhesion preventing plate, wherein the adhesion preventing plate connected to the potential adjusting mechanism and an adhesion preventing plate adjacent to the adhesion preventing plate connected to the potential adjusting mechanism among the plurality of adhesion preventing plate are disposed at an interval of 0.5 mm to 3.0 mm, and characterized in that the radio frequency sputtering power supply and / or the potential adjusting mechanism are configured to decrease the plasma density stepwise, in a case where the radio frequency sputtering power supply is turned off after the piezoelectric film reaches a predetermined thickness.