To make an internal combustion engine provide good response drive, simplify a structure of an intake device provided with an air cleaner purifying intake air to the internal combustion engine and facilitate forming work.

The air cleaner 16 is connected to the internal combustion engine 10 and an air lead-in passage 26 extending from an outside of an cleaner case 20 of the air cleaner 16 to an element 21 side is formed on the cleaner case 20. The air lead-in passage 26 is formed on the cleaner case 20 to pass through the cleaner case 20 in an upstream side of the element 21. A communication opening 27 for making a middle part of the air lead-in passage 26 communicate to the element 21 is formed on the cleaner case 20. The air lead-in passage 26 is two dimensionally bent on a virtual plane surface 31. Center axes 37, 38 of each end part of the air lead-in passage 26 are crossed each other and a center axis 40 of the communication opening 27 is arranged on the virtual plane surface 31.