Layer thickness is the major parameter of the 3D printing process that should be investigated for digital forensic purposes. However, despite its importance, there have been no studies yet on this parameter of layer-manufactured models. This Letter focuses on an effective estimation of layer thickness parameters for layer-manufactured models. Based on the analysis results of the scanned 3D model, the proposed method provides a new solution for estimating the layer thickness. Regarding potential applications including multimedia forensics, the proposed estimator would be useful in a variety of fields.