Composite particles composed of waste polymer and waste paper fibers were prepared by a chemical crushing method. Newspaper was used as paper fiber. Polystyrene beads, which were prepared by suspension polymerization, were adopted as the waste polymer. In the experiment, in order to adjust the affinity for the polymer solution, paper fibers were pretreated using a few treatment agents. It is found that the mechanical strength of the composite particles increases by addition of fibers. Furthermore, it is found that there is an optimum concentration for each treatment agent.