To reinforce the interlaminar of laminated composites, a novel method was proposed by the authors [1]. In this method, whiskers were added in the matrix resin to reinforce the interlaminar, and the orientation of the whiskers were magnetically con trolled to improve the reinforcement efficiency. In this paper, mode I (cleavage) inter laminar fracture toughness was shown to be remarkably improved as a result of the addi tion of oriented whiskers to the direction of the plate thickness. Whereas, mode II (inplane shear) interlaminar fracture toughness and interlaminar shear strength (ILSS) were not raised. Parameters of interlaminar reinforcement such as volume fraction of whiskers and whisker dimension were also discussed for exploring the optimum condition.