For terahertz microscopy, we propose an original approach with Planar Goubau Lines (PGL) by taking advantage of the confinement around the metallic strip. The idea is to obtain an alternative to the illumination by free space wave. The structure is fabricated on a thin high resistivity silicon substrate and it is composed of two CPW-PGL transitions, two bendings and a coupling region between the two disconnected PGL sections. The sample is placed at the vicinity of the tapered tip. We have characterized the on-chip THz microscope with and without samples.