Micro slits have been designed between micro cylindrical pillars to sort biological cells. Micro cylindrical pillars of 0.02 mm diameter and 0.055 mm height were fabricated on the glass plate using the photolithography technique. Variation was made on the gap between pillars: 0.01 mm, 0.02 mm, 0.03 mm, and 0.04 mm. The micro pillars are set in the flow path between parallel plates, of which dimension of the cross section is 5 mm width and 0.055 mm height. Three kinds of biological cells were used in the test alternatively: C2C12 (mouse myoblast cell line originated with cross-striated muscle of C3H mouse), Hepa1-6 (mouse hepatoma cell line of C57L mouse), or swine red blood cell. The suspension of cells was introduced into the slits by the syringe pump at the flow rate between 0.4 and 500 cm3/hour. The deformation of the cell at the slit can be observed by the microscope. The experimental results show that the designed slit has capability for sorting cells according to the size and deformability of the cell.