A molding device suitable for performing at least one of injection molding of preforms and blow molding of the preforms includes a pitch changing device including: N holding units capable of holding the preforms and arranged at a predetermined pitch in a predetermined direction, N being inter equal to or larger than 2; a coupling unit coupling the holding units adjacent to each other such that the pitch is changeable; a drive unit configured to generate a predetermined drive force; and a drive force transmission unit configured to transmit the drive force to each of one end-side and the other end-side, in the predetermined direction, of the coupled N holding units. The one end-side and the other end-side are configured to be moved in the predetermined direction by the drive force to change the pitch.