To provide a fuel reforming catalyst for an engine and a reformer for improving fuel efficiency which are capable of remarkably saving fuel consumption by promoting reforming of fuel for a diesel engine and a gasoline engine.

The fuel reformer of an engine for improvement of fuel efficiency comprises an octagonal cylindrical filter 2 filled with a proper amount of ceramic balls 1 which emit far infrared rays and ions, made of polyacetal, and having a large number of small holes in the outer circumference and is thrown to a fuel tank 3 and immersed in the fuel.