In this study,theviscosityofunidirectionalCFRTP laminatesnearthemelting point was evaluated to discuss therelationship between thethermalfusion conditionsand theflowoffiberand matrix.Thelaminateswereregarded asa fluid flowing in a direction perpendicularto thefiber.The microscopicflowofthefiber and matrix nearthemelting point wasobserved during a parallelplate compression test. Based on this observation, viscosity and flow properties were evaluated by the finite element method. The results of the parallel plate compression test showed that the test conditions and the decrease in the thickness of the laminates are related to the apparent viscosity of the unidirectional plate. In addition, cracks in the direction of the maximum shear stress were detected via in situ observation near the melting point of the matrix. The occurrence of this phenomenon depended on the apparent viscosity of the unidirectional laminates and it was found that no cracks occurred when the apparent maximum viscosityofthe unidirectional laminates was lower than a certain threshold.