PROBLEM TO BE SOLVED: To provide a coextrusion biaxially stretched polyester film having good heat sealability and peelability, showing good adhesiveness with respect to another polymer layer, a metal layer, a printing layer and the like and suitably usable as a lid material for a tary comprising CPET or CPET/APET. SOLUTION: In this coextrusion biaxially stretched polyester film composed of a base layer B and a heat-sealable outer layer A, the outer layer A can be peeled after heat-sealed to a CPET layer or a CPET layer/APET layer (1) and composed of a 80-99 wt.% of a polyester (a) and 1-10 wt.% of particles with an average particle size d 50 of 2.5-12 μm (2). The polyester (a) comprises a polyester having 12-89 mol% of an aromatic dicarboxylic acid unit and 11-88 mol% of an aliphatic dicarboxylic acid unit, and the ratio of the average particle size of the particles contained in the outer layer A and the thickness of the heat-sealable outer layer A is 1 or above and the base layer contains MXD 6. COPYRIGHT: (C)2005,JPO&NCIPI