PURPOSE: To decrease the size of a device and a cost, by a method wherein, in a titled carburetter of a variable venturi type, a negative pressure responding valve, opening and closing a suction passage, and a slide throttle valve are positioned facing each other in a throttle valve guide cylinder connected to a suction passage running through a carburetter body.

CONSTITUTION: A throttle valve guide cylinder 3 is connected to the middle part of a suction passage 2 running through a carburetter body 1, and a negative pressure responding valve 10 and a slide throttle valve 11 are positioned facing each other in the guide cylinder 3. The negative pressure responding valve 10 is formed with a square venturi forming part 10A and a flat laminar part 10B formed to the one side part thereof, and the upper end part of a cylinder part 10C erected to the venturi forming part 10A is connected to a diaphragm 13. The slide throttle valve 11 is formed in a boxform manner, a coupler 17A, being the end part of a control piece 17 controlled by an operator, is engaged with guide grooves 11B machined in two side end parts of a flat laminar part 11A being the one side part of the slide throttle valve, and rotation of the control piece 17 around a shaft 18 causes opening and closing of the slide throttle valve.