PURPOSE: To inexpensively provide a constant vacuum type carburetor equipped with an automatic starter and an air cut valve device and to make the carburetor small in size.

CONSTITUTION: A fitting flat area 90 is formed on one side of a carburetor body 1 where an air chamber recessed part 91 is opened and a fitting flat area 95 is formed on a cover body 94 where a pressure chamber recessed part 96 is opened. The fitting flat area 95 of the cover body 94 is arranged on the fitting flat area 90 of the carburetor body 1 through a partition body 60 and an air chamber 63 is formed by the partition body 60 and the air chamber recessed part 91, while a pressure chamber 62, in which a spring 64 is contractively provided, is formed by the partition body 60 and the pressure chamber recessed part 96. A slow speed air introduction passage 66 equipped with a second slow speed air jet 68 and a second slow speed air passage 67 communicating with the slow speed air passage are opened in the interior of the air chamber 63. The second slow speed air passage 67 is opened and closed by an air control valve 69 which synchronously operates with the partition body 60. The cover body 94 is arranged with a starting valve 49 which is actuated by a wax member 51 and automatically opens and closes a starting fuel passage 93, a starting air passage 97 and a starting air-fuel mixture passage 98.