PURPOSE: To improve the wear proof and crushing strength and consequently the durability of the spongy spherical body by a method wherein the spongy spherical body for cleaning the inside of the heat pipe of heat exchanger is formed with non-woven fabrics made of plastic fibers.

CONSTITUTION: The titled spherical body is formed of plastic fibers. The plastic fibers with excellent wear proof and hot water proof are preferable. Nylon fibers, Teflon fibers or the like are acceptable and one or no less than two kinds thereof mixed with one another are used. The spherical body is made either by laying out of non-woven fabrics formed beforehand in the fixed form or by injecting molten resin composition for manufacturing plastic fibers from a moving nozzle in order to fusion-weld the intersecting parts of the fibers. The spherical body within which also abrasives are contained, is preferable.