PURPOSE: To make it possible to stably perform the purification by mounting annular filter elements at both sides of a partition plate made of a resin or a metal so that the element intersects rectangularly the surface of the partition plate, in an annular air cleaner element structure.

CONSTITUTION: A fresh air inlet path 14 is connected to an air cleaning chamber 6, and gasoline vapor of a cleaning chamber 5 passes through a filter element 1a. The vapor once leaves the cleaning chamber 5 and enters an annular chamber 15. However, before the vapor flows into the cleaning chamber 6 via a filter element 1b at the upper part of the partition plate 2, the vapor flows out to the outer part from an air cleaner nose 9. Therefore, the cleaning chamber 6 is constantly cleaned during the driving of the engine and during the stoppage of the engine. Accordingly excessively concentrated gaseous mixture at the time of starting and idling can be formed into a proper gaseous mixture. Thus, the starting characteristic and idling stability can be improved. Moreover, a thermovalve 12 is closed at the low temperature time and opened at the high temperature time.