The ^<35>Cl NQR of tetrachlorothiophene has been observed and the Zeeman effect on a single crystal has been examined. This compound yields four lines at room temperature. These lines are divided into two distinct groups, i.e., two lower frequency lines (36.90 and 36.93 MHz) and two higher frequency ones (37.63 and 37.68 MHz). On the basis of Zeeman analysis, the lower lines are assigned to the Cl atoms at the 3- and 4-positions and the higher ones to those at the 2- and 5-positions. The angles between the C-Cl bonds have been deduced and it has been revealed that four C-Cl bonds in the molecule are nearly coplanar. From the distribution of the zero-splitting loci, it has been determined that the crystal of TCT belongs to an orthorhombic system.