A subject for the invention is to provide a process of producing a dimeric alcohol in high yield with high selectivity by the Guerbet reaction conducted using an alcohol having 4 or less carbon atoms as a starting material in the presence of a complex including a transition metal and of a base. The invention relates to a process of producing an alcohol which includes dimerizing a starting-material alcohol having 4 or less carbon atoms in an environment having a partial hydrogen pressure of 0.1 MPa or higher.