This study empirically examined the influences of electrospinning process factors (applied voltage, feed rate of the polymer solution and tip-to-collector distance) and the polymer solution concentration on the diameters of electrospun polyacrylonitrile (PAN) nanofibers. To examine this, the polymer solution concentration, applied voltage, feed rate of the polymer solution and tip-to-collector distance were specified as parameters with four levels. In order to optimize these parameters, Taguchi's L-16 orthogonal design (4 parameters, 4 levels) was applied to the experiential design. In order to describe the optimum production conditions for electrospun PAN nanofibers, the signal-to-noise (S/N) ratio was used, which was calculated from the diameters of electrospun PAN nanofibers using the "smaller-the-better" approach. By using the S/N ratio response results, the most influential parameter determining the nanofiber diameter was identified as the polymer solution concentration. The nanofiber diameter at the optimum conditions was 163.6 nm. In addition, homogeneous nanofibers with no observed beads were obtained by means of the newly designed adjustable rotary plate collector. In conclusion, the Taguchi technique was seen to be an efficient technique to optimise the crucial electrospinning process factors used in nanofiber production.