A single-crystal manufacturing apparatus comprising at least: a main chamber configured to accommodate a crucible; a pulling chamber continuously provided above the main chamber, the pulling chamber into which a grown single crystal is pulled and accommodated; a gas inlet provided in the pulling chamber; a gas flow-guide cylinder downwardly extending from a ceiling of the main chamber; and a heat-insulating ring upwardly extending from a lower end portion of the gas flow-guide cylinder with a diameter of the heat-insulating ring increased so as to surround an outside of the gas flow-guide cylinder, wherein at least one window is provided in a region between 50 and 200 mm from a lower end of the gas flow-guide cylinder, and an opening area of the window accounts for 50% or more of a surface area of the region between 50 and 200 mm from the lower end of the gas flow-guide cylinder.