A heat pipe includes a heat receiving section, a heat transfer section, and a heat dissipation section. A groove structure is formed inside the heat pipe and extends from the heat receiving section to the heat dissipation section. The groove structure includes at least an axially-extending parallel portion and a non-axially-extending parallel portion. The axially-extending parallel portion includes a plurality of internal groove segments extending parallel in an axial direction of the heat pipe and the non-axially-extending parallel portion includes a plurality of groove segments extending from the axially-extending parallel groove segments in a parallel manner in a direction different from the axial direction.