In this study, nanofibers of polyurethane and thermoplastic polyurethane were produced by electrospinning method and the average diameters of the produced nanofibers were analyzed by the scanning electron microscopy. Then, the effect of several parameters such as applied voltage, polymer concentration, flow rate and solution temperature on the average diameter of nanofibers were explored on electrospinning process. In polyurethane nanofibers, the average diameter of 87 nm was achieved by decreasing the concentration of solution from 12% to 10% and in thermoplastic polyurethane nanofibers, the average diameter of 88 nm was achieved by increasing temperature at 10 kV. The results of this work can be used to produced ultrafine PU and TPU nanofibers and extend their applications.