A polytetrafluoroethylene (PTFE) surface is smooth and biologically inert, so that cells cannot attach to it. In this study, we modified a PTFE surface using ion-beam irradiation with various ion fluences to help cell adhesion. To investigate the relationship between the cell-material interaction and physicochemical properties, we observed the irradiated PTFE surface using scanning electron microscopy (SEM), attenuated total reflectance/Fourier transform infrared (ATR/FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and measured the droplet contact angle. From the SEM observations, micro pores formed on a wrinkled surface at lower fluences, while a large number of protrusions were formed at higher fluences. The contact angle of water decreased from 110° to 90° at a fluence of 1 x 1015 ions/cm2, and increased again up to 160° at higher fluences. The ATR/FT-IR and XPS analyses showed that =C=O, -OH and -C=C- bonds were introduced on the surfaces irradiated using low fluences, and at higher fluences, the number of these bonds was reduced, but they remained at the top of the protrusions. On culturing L929 cells on the irradiated surfaces, cell adhesion, spreading, and proliferation were observed on all the irradiated surfaces, although the properties were different for each surface. Using these modified surfaces, we fabricated a substratum that could culture single cells.