To provide a polyester fiber structure having excellent deep color dyeability.

The polyester fiber structure contains a polyester fiber having recesses satisfying the conditions (1) to (4) on at least a part of the single fiber surface. (1) The maximum diameter in the fiber axis direction is ≥0.01μm and <0.5μm, (2) the maximum diameter in the direction perpendicular to the fiber axis is ≥0.1μm and <1μm, (3) the maximum diameter in fiber axis direction is smaller than the maximum diameter perpendicular to the fiber axis, and (4) the number of the recesses is 20-200/9μm2. The method for the production of the polyester fiber structure contains the thinning treatment of a fiber structure containing a polyester fiber under conditions satisfying the requirements (1) to (3). (1) The pH of the treating bath is 10.5-12.5, (2) the weight-mol concentration of the alkali in the treating bath is 0.01-0.5 mol/kg, and (3) the temperature of the treating bath is 130-180°C.