The image heating apparatus includes a flexible sleeve including a stainless base layer; a heater being in contact with an inner circumferential surface of the flexible sleeve; and an elastic roller being in contact with an outer circumferential surface of the flexible sleeve and forming a nip portion with the heater, in which: a recording material bearing an image is heated while being pinched and conveyed at the nip portion; and the stainless base layer has an outer diameter of 18 mm to 24 mm and a thickness of 25 .mu.m to 30 .mu.m, and includes an outer circumferential surface being subjected to a blasting process. Bu the present invention, an image heating apparatus is capable of ensuring durability and a flexible sleeve used for the image heating apparatus.