In a reaction apparatus of the chlorosilanes for heating a reaction portion that is a section from the bottom end portion to a specified height in the carbon reaction vessel and that has an inside face to which silicon has deposited, and for reacting the chlorosilanes by making the chlorosilanes and hydrogen to come into contact with the inside face of the reaction portion, a gas penetration preventing processing for preventing the chlorosilanes supplied to the reaction vessel from penetrating a pipe wall of the non reaction portion in the reaction vessel is carried out to the inside face and/or the outside face of the non reaction portion on the side upper than the reaction portion in the reaction vessel.