The purpose of this research was to study the fatigue behaviour and the test method for S2 glass fibre reinforced plastic under an interlaminar shear fracture mode. Fatigue tests were carried out under the short beam shear (SBS) condition of three point bending. The main results obtained are as follows. 1) Interlaminar shear fatigue fracture was realised for SBS specimens with the span ratio of L/t = 4 and 3.5. 2) Fatigue crack propagation was detected during interlaminar shear tests by using scanning acoustic tomography. 3) In interlaminar shear fatigue tests under the condition of varying stress amplitude, the cumulative fatigue damage calculated by Miner's law was approximately unity when the scattering of fatigue data was taken into consideration.