PURPOSE: To prevent a danger of ignition to an overdense fuel remaining in a suction path by constituting so that a hot wire is not heated to a high temperature, in case when it is detected that a mixture becomes overdense abnormally due to an overflow of stored evaporating fuel of a canister, etc., and an engine has stopped.

CONSTITUTION: A hot wire 24 of a hot wire type air flow meter 23 is provided in a suction path 22 of an internal-combustion engine 21. An incinerating means 25 makes a high voltage current flow to the hot wire 24 immediately after an ignition switch becomes off by an ignition detecting means 26. A canister device 27 supplies a purge air containing an evaporating fuel into the suction path 22 in accordance with an operating state of the internal combustion engine 21. Also, basing on a detecting signal from a stop detecting means 28 for detecting a stop state of the engine 21, and a detecting signal from the ignition detecting means 26, a conduction control means 29 makes a high voltage current flow to the hot wire 24 by operating the incinerating means 25, in case when the engine 21 is not in a stop state, and on the other hand, does not operate the incinerating means 25, in case when the engine 21 is in a stop state, immediately before the ignition switch becomes off.