A flexible two-phase conversion heat transfer device includes a main body enclosing a chamber. A working liquid is received in the chamber. A capillary structure body is disposed in the chamber. The main body has at least one bellows section. The bellows section has multiple waved stripes. The waved stripes at least have a waved stripe feature including a waved stripe height or a waved stripe width or a waved stripe pitch between each two adjacent waved stripes. By means of the different waved stripe features, the main body is bendable by an angle ranging from 0-180 degrees without interference between the waved stripes.