Intake structure for internal combustion engine

The intake structure for an internal combustion engine includes: a collision surface (25) configured to face an inlet (4) of a carburetor (3); a deflecting surface (29) configured to deflect a blowback flow, which is to diffuse after colliding against the collision surface (25), in one direction along the collision surface (25); a receiving surface (30) configured to receive the blowback flow deflected by the deflecting surface (29); and a fuel-accumulating surface (31) formed below the collision surface (25). A first clearance between an air-guiding direction distal end (29a) of the deflecting surface (29) and the receiving surface (30) is brought into communication to a downstream side (13) of a filter (12) of an air cleaner (5) in a fresh-air intake direction so as to act as a main intake passage for fresh air.