Disclosed is a stable organic thin film transistor having good switching property and a process for manufacturing an organic thin film transistor by a simple method. The organic thin film transistor comprises a substrate and provided thereon, at least a source electrode, a drain electrode, an organic semiconductor connecting the source electrode and the drain electrode, a gate electrode, and an insulating layer composed of a plurality of layers, the insulating layer being provided between the gate electrode and the organic semiconductor, wherein the organic thin film transistor comprises a mercapto group-containing compound represented by the following formula (I), (R)n—Si(A)3-n-(B)  Formula (I) wherein R represents an alkyl group having a carbon atom number of not more than 8; A represents an alkoxy group or a halogen atom; B represents a substituent containing an SH group; and n is an integer of from 0 to 2.