Heating part, substrate processing apparatus and method of manufacturing semiconductor device

The invention provides a structure for reducing uneven temperature of a gas pipe heated by a heater. A heating part of covering and heating a gas pipe includes: a thermal insulation portion disposed outside a heat generation body; an enclosure configured to enclose the thermal insulation portion and the heat generation body; a fastening part installed outside the enclose and configured to fasten one end portion and the other end portion of the enclosure in a state in which the one end portion and the other end portion of the enclosure adjoin each other; and a temperature sensing part disposed at the side of the gas pipe with respect to the enclosure at a position facing a surface of the gas pipe and formed in a plate shape with a major surface thereof oriented toward the gas pipe. 本发明提供种降低由加热器加热的气体管的温度不均的结构。具有：隔热部，其配置在发热体的与气体管相反的侧；包围体，其将隔热部及发热体包围；固定部，其设在包围体的外侧，且在包围体的端侧和另端侧相邻的状态下将端侧和另端侧固定；和温度检测部，其在比包围体靠气体管侧配置在与该气体管相对的位置上，并将气体管侧作为主面而形成为板状。