Poly L lactic acid (PLLA) is attracted a great deal of attention. Because PLLA is a plant-derived plastic and is a bio-compatible one. And also, PLLA has piezoelectricity. Therefore, it is expected that the use of PLLA reduces environmental load in piezoelectric sensors and actuators for consumer applications. For sensor and actuator applications, Micro Electro Mechanical Systems (MEMS) technologies are important. In the fabrication of MEMS by PLLA, ion beam irradiation is consider to be a valuable tool for maskless patterning of high-aspect-ratio structures in the micro- and nanoscale. Proton Beam Writing (PBW) is also expected to apply for the micro fabrication process. In this report, PBW is applied for the micro fabrication of PLLA (poly L lactic acid) polymers which is piezoelectric polymers, plant derivative and has bio-adaptability. PLLA bulk and film are irradiated with 1MeV proton beam (PB). After beam irradiation, the samples are developed by ammonia liquid as the developing solution. As a result, the micro line of 3μm in width and 20μm in depth is fabricated successfully. Finally, the basic piezoelectric polymer actuator is fabricated.