A flat heat pipe includes a casing and a wick structure received in the casing. The casing has a first lateral portion and a second lateral portion. Each of the first lateral portion and the second lateral portion has a C-shape configuration, and the second lateral portion has an opening facing an opening of the first lateral portion. The wick structure is attached to an inner surface of only one of the first and lateral portions of the casing. The inner surface of the other of the first and second lateral portions without the wick structure attached thereto defines a first vapor channel, and an inner surface of the wick structure defines a second vapor channel. The first vapor channel has a height greater than the second vapor channel.
