To provide a fuel combustibility improving structure of an internal combustion engine for easily performing maintenance, by using an easily manufacturable combustibility activation member.

The combustibility activation member 1 is constituted by forming a thin film layer 3 including titanium oxide on the outside of nonwoven fabric 2, by painting tourmaline powder in this nonwoven fabric and painting zirconium dioxide powder and silicon dioxide powder inside, with the nonwoven fabric 2 as a structure. At least one of silver or copper is included in the thin film layer 3 beside the titanium oxide. The combustibility activation member 1 is installed on an iron outer wall of a fuel tank, and a magnetic field is formed in an existing area of the fuel tank and the combustibility activation member by a magnetism generating device arranged in the vicinity of the fuel tank.