Polylactic acid (PLA) is a bio-based and biodegradable polymer currently used in a wide range of packaging, medical, and industrial applications. PLA is also envisaged for the development of sustainable products for general public, including electronic devices. For these applications, the knowledge of the dielectric properties is required, in particular for high frequency electronics. In this letter, coplanar waveguides are realized on a PLA substrate in order to characterize its complex permittivity from 0.5 to 67 GHz. To avoid putting the PLA in contact with strong chemicals or solvents, a line transfer technique combined with photolithography process has been developed to realize the test structure. The propagation constant is calculated by de-embedding techniques using S-parameter measurements. Finally, finite element method analysis is used to determine the real permittivity (epsilon(r)) and loss tangent (tan delta) of the PLA substrate.