Provided are a plasma treatment method and a plasma treatment device capable of forming a silicon nitride film having high compressive stress. In the plasma treatment method for depositing the silicon nitride film on a process target substrate by use of plasma of raw material gas containing silicon and hydrogen and of nitrogen gas, ion energy for disconnecting nitrogen-hydrogen bonding representing a state of bonding between the hydrogen in the raw material gas and the nitrogen gas is applied to the process target substrate so as to reduce an amount of nitrogen-hydrogen bonding contained in the silicon nitride film.