PURPOSE: To supply clean air having little dust to an air cleaner provided in an engine cover covering an engine.

CONSTITUTION: The air cleaner case 86 of an air cleaner 67 is integrally formed on the side wall of an engine cover 1 covering an engine E. Air taken-in from an inlet port 69 provided on the rear part of the engine cover l is blocked by partitioning ribs 92 and 93 formed between the air cleaner case 86 and the inner wall of the engine cover 1 to detour and introduced in the inside of the air cleaner case 86 from an inlet port 86 provided on the opposite side to the inlet port 69 to the air cleaner case 86. During the flow of air taken-in into the inside of the engine cover 1 detours, dust included in the flow is dropped to supply clean air to the air cleaner 67.