According to an embodiment, there is provided a heat spreader including an evaporation portion, a first condenser portion, a working fluid, and a first flow path. The evaporation portion is arranged in a first position. The first condenser portion is arranged in a second position, the second position being arranged apart from and higher than the first position. The working fluid evaporates from a liquid phase to a gas phase in the evaporation portion, and condenses from the gas phase to the liquid phase in the first condenser portion. The first flow path is made of a nanomaterial, has hydrophobicity on a surface, and causes the working fluid condensed to the liquid phase in the first condenser portion to flow to the evaporation portion by a gravitational force.