Nanoimprint technology is attractive for fabrication technique of patterns below 100-nm dimension. We have already attempted to replicate a mold pattern onto a liquid polymer solidified with UV light irradiation in order to avoid a deformation due to thermal expansion and succeeded to transfer pattern with 60 nm line-width. However the transfer pattern had a fluctuation in line width, mainly due to fluctuation of mold pattern itself. It is strongly required to demonstrate the ultimate accuracy of the replicated pattern in photo-curable nanoimprint and to investigate a line edge roughness (LER). In order to make clear this problem, we examined characteristics of the LER in photo-curable imprint using a mold with atomically flat sidewall.