We developed a novel thin shear-stress sensor, using electrolyte as a conductive element. The sensor is composed entirely of flexible materials, such as plastic sheets, silicone rubber, and the electrolyte solution. The electrolyte is enclosed in a cell containing a central electrode surrounded by four peripheral electrodes. The sensor is designed so that the conductance between these electrodes is changed by shear stresses resulting from cell deformation. The diameter (excluding the wiring pattern) and the thickness of the fabricated sensor are 29 mm and 2 mm, respectively. We employed LiCl in ethylene glycol as the conductive element, and the measurement conditions were chosen to minimize electrochemical damage to the electrodes. A sinusoidal voltage wave of 160 mV (peak-to-peak) at a frequency of 5 kHz was applied between the center electrode and each peripheral electrode, and the resulting current provided the sensor response. The new sensor successfully detected not only the magnitude of the shear force, but also its direction.