An exemplary flat heat pipe with an evaporator section and a condenser section includes a hollow casing, and a first wick structure and a second wick structure in the casing. The second structure contacts an inner surface of the casing at the evaporator section. The first structure at the evaporator section includes a first contact portion contacting an inner surface of the second structure, and a first isolated portion from the inner surface of the second structure. The first isolated portion and the inner surface of the second structure define a first channel therebetween. The first structure at the condenser section includes a second contact portion contacting the inner surface of the casing, and a second isolated portion from the inner surface of the casing. The second isolated portion and the inner surface of the casing define therebetween a second channel communicating with the first channel.