To increase the capacity of an air cleaner by providing air ducts removably and airtightly connected to the insertion hole of an air cleaner through a communication hole connected to an intake port and communicating the inside and outside of the branch section of a main frame.

Rear ducts 27b, 28b are connected to the base box 21 of an air cleaner 17 removably in the axial direction. When the air cleaner 17 is removed from the rear ducts 27b, 28b, the rear ducts 27b, 28b are moved to a front cowling 14 side in the axial direction and drawn from the air cleaner 17, and the air cleaner 17 can be easily removed. The air cleaner 17 itself is not required to be moved along the axial direction in the narrow space inside the fork branch sections 2b, 2c of a main frame 2, the capacity of the air cleaner 17 can be increased, and the interval with the fork branch sections 2b, 2c of the main frame can be shrunk.