Biaxially stretched polyester film and method for producing same

A biaxially stretched polybutylene terephthalate film comprising a polyester resin composition containing 60% by mass or more of polybutylene terephthalate, wherein

• the film comprises an alkaline earth metal compound and a phosphorus compound, and the mass ratio (M2/P) of alkaline earth metal atom (M2) to phosphorus atom (P) is 1.2 or more and 5.0 or less,
• a melt specific resistance of the film is 0.10×108 Ω·cm or more and 1.0×108 Ω·cm or less,
• a peak temperature of tan δ as determined by the dynamic viscoelasticity measurement at 10 Hz of measurement frequency is 60° C. or more and 100° C. or less in both the MD direction and the TD direction, and a peak value of tan δ is 0.080 or more and 0.15 or less in both the MD direction and the TD direction.