The electron momentum spectra of outer valence orbitals 9a1+5b2 of thiophene (C4H4S) have been studied by binary (e, 2e) electron momentum spectroscopy (EMS), at an impact energy of 1200 eV plus binding energy, and symmetric non-coplanar kinematics. The experimental momentum profile of the summed orbitals is compared with the theoretical momentum distributions calculated using Hartree-Fock (HF) and density functional theory (DFT) methods with various basis sets. The experimental measurement is well described by the HF and DFT calculations, and the calculations using the larger basis sets including diffuse and polarization functions give better descriptions of experiments.