To provide a magnet cap which is easily manufactured simply in a mass production and in which a magnetizing force is raised by increasing a magnetic flux by broadening a magnetic flux surface.

The magnet cap 1 comprises a magnet magnetized at the head of a drain bolt (drain plug) and provided in an oil pan 10 or an oil cleaner or the like of a vehicle, which magnetizes an iron powder at the end 13a of the bolt (plug) 13 to capture and separate the powder 6 in an oil 14. The cap 1 is formed in a cylindrical shape. The cap 1 further comprises: a body 1 having at one end with a corner and opened at the other end in the cylindrical shape; a plate 3 for guarding the lower surface of the magnet 4 stored in the body 2; the magnet 4 for forming a magnetic field by generating the line of magnetic force, and a cover 5 for protecting the upper surface of the magnet 4.

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