To eliminate troublesomeness in a starting operation of a carburetor in which a throttle valve 4 and a measure stylus 11 of a fuel associate with each other and a high density air-fuel mixture at starting is obtained by a choke mechanism C.

This carburetor comprises: a lift up mechanism L which changes the measure stylus 11 from an idle position to a starting position in association with a choke valve closing operation of the choke mechanism C; a fast idle mechanism M which changes the throttle valve 4 from the idle position to a starting opening; and a locking mechanism N which holds the starting position and the starting opening even after a choke function release. The locking mechanism N is released with a full open direction operation of the throttle valve 4. Starting and warm-up are carried out only by a choke operation, and thereafter, an engine operation is carried out by a normal accelerator operation.