The present invention provides a pharmaceutical composition and method for regenerating nerves and treating neurological diseases based on nerve regeneration. The present invention employs a substance, such as Pep5, PKC, IP3, Rho, Rho GDI, Rho kinase, or the like, which are involved in a p75 signal transduction pathway, or an agent capable of specifically interacting with any of these substances to block or suppress the p75 signal transduction pathway, thereby stopping inhibition of nerve regeneration. As a result, nerve regeneration is resumed. The present invention is also the first to disclose that the PTD domain is useful as an agent for nerve regeneration.