To stabilize warming-up operating state by automatically controlling opening of a throttle valve larger than the usual idle opening without performing a special operation for appropriately strengthening spring force of a governor spring during warming-up operation of an engine.

In this throttle valve control device of a carburetor provided with the governor device G connected to a throttle lever 23, a choke return spring 21 for energizing a choke lever 22 toward a choke valve 19 closing side is connected to the choke lever 22, and an auto-choke device A is arranged opposite to the choke lever 22, and a throttle valve closing regulating means 58 is provided between the throttle lever 23 and the choke lever 22. During warming-up operation, when spring force of the governor spring 54 is adjusted to the minimum, the choke lever 22 regulates closing of the throttle valve 20 through the throttle lever 23 with the spring force of the choke return spring 21.