A highly reliable vacuum heat insulating material having excellent processability, handleability and heat insulating performance, and a heat insulating box using the vacuum heat insulating material are provided. In the vacuum heat insulating material with the inside in an approximately vacuum state by sealing a core material 5 having a structure wherein plural pieces of fiber assembly 1 are laminated by a gas-barrier outer cover material 4, by using long fiber for the core material, fiber dust or remaining fiber by cutting is prevented from protruding into a sealing portion of the outer cover material from a cut surface of a sheet or an opening portion, and sealing failure is reduced. Further, since the core material is structured so as to be wound continuously from an inner side toward an outer side, the vacuum heat insulating material is easily manufactured, and excellent in handleability.