PURPOSE: To prepare a polyester container with excellent appearance in good productivity without generating connection defficiency, whitening phenomenon or the like in a connected part by forming a pore part of the container by using a specific mold.

CONSTITUTION: To a position of a barrel mold 13 corresponding to a pore part and a fin part of a container 1, a metal mold 11 having a slidable press member 17 provided along a sleeve 18 thereof is used. An inner temp. of the metal mold 11 is adjusted to a temp. of a glass transition point or more and other part of said metal mold is adjusted to a glass transition point and, thereafter, a resin parison is enclosed in a carity 15 to carry out biaxial orientation. Next, a pressure member 17 is pushed into the barrel mold 13 to closely adhere a part of an intermediate wall part 20C' and, thereby, a closely adhered part 23 is formed. Subsequently, the molded object 20' is taken out from the mold and the closely adhered part 23 is punched and cut by using a cutter 27 comprising a blade part 24 having a temp. higher than that of a die 25 and a m.p. of the resin to form a pore part 4 as well as to fuse an end flange part 8 of a fin part 6 by heating.