This paper describes a delayed fracture model for transverse cracking in CFRP cross-ply laminates under creep loading on the basis of the slow crack growth (SCG) concept. First, an SCG-based fracture model for a crack in a brittle material was established in conjunction with a probabilistic fracture model using the three-parameter Weibull distribution. Secondly, the above probabilistic SCG model was applied to transverse cracking in cross-ply laminates under creep loading. The shear lag analysis was employed to consider the stress and the length of the unit element in the transverse layers. The transverse crack density was expressed as a function of applied stress and time when the parameters in the Paris law and the Weibull distribution were given in addition to mechanical properties. Unknown parameters were determined from experimental data of the static tensile and static fatigue tests. Reproduced transverse crack density at various applied loads agreed well with the experimental results.