To obtain a polyester fiber having excellent raising property when producing a napped fabric and suitable for producing the napped fabric excellent in napping property and soft feeling and a napped fabric using the fiber.

This polyester fiber is mainly composed of a polyester and simultaneously satisfies the following characteristics (1): 2%≤0.2≤30%, (2): ISa/ISb≥0.9, and (3): Im/(dtpf)2≥450 [wherein 0.2 is integrated parameter of a structure; ISa is an initial tensile modulus (cN/dtex) after dry heat treatment; ISb is an initial tensile modulus (cN/dtex) before dry heat treatment; Im is a cross sectional secondary moment (μm4); and dtpf is single yarn fineness (dtex)].