In effecting the stretching by using a stretch rod in a method of producing a biaxially stretched polyester bottle, the air is blown into the preform at such a flow rate that the preform does not come in contact with the stretch rod but the end thereof and does not come in contact with the surfaces of the mold, either. There can be produced a biaxially stretched polyester bottle having an average thickness of about 0.05 to about 0.2 mm or having a further decreased thickness using a resin in decreased amounts and having a decreased weight without developing burst or whitening caused by over-stretching, without forming ring-like thick portion yet maintaining a good yield and efficiency.