Is it possible to distinguish cells with minimally invasive methods according to the characteristics of cells when moving through flow paths in vitro? A microflow-channel with microgrooves 45 deg diagonal to the mainstream direction has been manufactured by photolithography technology. The flow path between the two transparent polydimethylsiloxane disks (0.05 mm high, 1 mm wide, and 25 mm long) has rectangular microgrooves (4.5 μm deep, 0.2 mm long) at the bottom with variations in groove widths (0.03 mm, 0.04 mm, and 0.05 mm). Deformation and orientation of floating mouse-myoblasts (C2C12) during passage over the microgrooves were measured. Experimental results show that the larger the shape change of the two-dimensional projected image in the groove, the smaller the angle change tends to be. This method may be applicable to classification by cell deformation.