It is provided that a polyester resin and a polyester resin composition that allow reduction of harmful outgas and can form a coating film having excellent characteristics such as curability, retort resistance, and processability. A polyester resin composition comprising: a polyester resin (A) having an acid value of 100 eq/ton or more and smaller than 500 eq/ton; and a polyester resin (B) having an acid value of 500 eq/ton or more, wherein a content of the polyester resin (A) is 55 parts by mass or more and 95 parts by mass or smaller, and a content of the polyester resin (B) is 5 parts by mass or more and 45 parts by mass or smaller when a total mass of solid contents of the polyester resin (A) and the polyester resin (B) is 100 parts by mass.