Conducted herein is a tensile fatigue test of the Hand lay-up GFRP and the fatigue strength and the stiffness degradation due to repeated loadings was investigated. The fatigue strength were assessed based on the S-N diagram, and it was clarified that the fatigue limit was 35% of the static strength. It was also found that the stiffness decreased significantly at the initial stage of repeated loading, and then gradually decreased. Furthermore, attempt was made to evaluate the stiffness degradation of the Hand lay-up GFRP using the existing prediction formula. It is found that the stiffness degradation in the case of fatigue fracture can be predicted and the constants used in the evaluation formula were proposed.