An apparatus for plasma treatment is capable of plasma-treating works of resin material by irradiating the surfaces of the works with a microwave discharge plasma within a vacuum reaction chamber. A plasma introducing port is formed in the wall of the reaction chamber. A plasma-irradiating pipe is connected to the plasma introducing port for injecting the plasma into the reaction chamber to irradiate th surfaces of the works. A discharge port is formed in the wall of the reaction chamber to reduce the internal pressure of the reaction chamber. A plurality of the works are rotated in relation to each other about a common axis, and also individual works are rotated independently from each other about their own axes.