The present invention addresses the problem of providing: a heat-bondable composite fiber which is capable of maintaining crimp stability even if high elongation remains, and which provides a nonwoven fabric with excellent bulkiness and shaping workability that enables following to a complicated shape or processing with a high fiber deformation stress; a method for producing this heat-bondable composite fiber; and a nonwoven fabric which uses this heat-bondable composite fiber.　A heat-bondable composite fiber which comprises a first component that contains a polyester-based resin and a second component that contains a polyolefin-based resin having a melting point that is lower than the melting point of the polyester-based resin by 15°C or more, and which has an eccentric core-sheath structure wherein, in a cross-section of the fiber perpendicular to the lengthwise direction, the second component occupies the outer periphery of the fiber. This heat-bondable composite fiber has an elongation at break of 200% or more, a three-dimensional apparent crimp, and a crimp elastic modulus of from 85% to 100%.