Biaxially-oriented polyester film and layered body

A biaxially-oriented polyester film being a layered film having at least a base material layer and two easily adhesive layers, wherein

• the base material layer and the two easily adhesive layers contain a polyester as a main component,
• the base material layer and the two easily adhesive layers are stacked in an order of the easily adhesive layer/the base material layer/the easily adhesive layer, and
• the biaxially-oriented polyester film satisfies all of (1) to (4) below:
• (1) a difference between reversible heat capacity differences ΔCp at around glass transition temperatures of the easily adhesive layer and the base material layer is 0.10 or more and 0.45 or less;
• (2) heat sealing strength between (a) an easily adhesive layer of the biaxially-oriented polyester film and (b) an easily adhesive layer of an identical biaxially-oriented polyester film is 0.5 N/15 mm or less;
• (3) a stress at 10% elongation F10 in each of an MD direction and a TD direction is 90 MPa or more and 160 MPa or less;
• and
• (4) a molecular orientation ratio measured by using a molecular orientation meter is 1.0 or more and 1.3 or less.