In this study, performance of matrix/binder isotropic spunbonded geotextiles which used in weak ground improvement was tested by laboratory and field scales. Also, 2 kinds of isotropic spunbonded geotextiles were prepared. One is matrix/binder structure using low melting PET copolymer (co-PET) fibers for web bonding. The other is consisted of sheath/core (co-PET/PET) fibers. Through index test, it is seen that performances of the sheath/core structure isotropic spunbonded geotextiles were more valid to be used for weak ground improvement than matrix/binder structure isotropic spunbonded geotextiles. However, through the drainage performance test to be simulated construction fields, sheath/core structure isotropic spunbonded geotextiles showed unstable in construction fields. The matrix/binder isotropic spunbonded geotextiles showed better results for the drainage test in construction field and the field test results were suitable for weak ground improvement. Keywords: Matrix/Binder Isotropic Spunbonded Nonwoven Geotextiles, Weak Ground Improvement, Matrix/Binder Structure, Sheath/Core Structure, Drainage Test