PURPOSE: To facilitate starting by LPG by providing the carburetor jointly using LPG-gasoline with a choke valve releasing mechanism which opens a throttle valve only by a minute angle even when a choke wire is pulled but does not close a choke valve.

CONSTITUTION: When an engine jointly using fuel of a different kind is started by using LPG fuel, a choke releasing lever 33 is turned in the counterclockwise direction when the choke wire 27 is pulled in the direction of the arrow while a choke releasing wire 32 is returned in the direction of the arrow, and the lever 33 is contacted with a second choke arm 31. Accordingly, even when a choke lever 23 is turned, a coil spring is only rolled in and a choke arm 28 cannot follow up the revolution of the lever 23 by contact between the arm 31 and the lever 33 in the choke arm 28, and the choke valve 21 is held as it is under the state of valve opening. The lever 23 opens the throttle valve 7 only by predetermined opening through a link 26, a throttle lever 25 and a throttle arm 29. Accordingly, a suction flow is generated in a barrel 3, a nozzle 2 is brought to negative pressure and LPG is supplied, and the carburetor is started easily.