The purpose of this study was to design a compression shear device for easy and fast measurement of the bonded shear strength of wood-based materials to replace the conventional method used to evaluate internal bond strength (IB). To assess the performance of this device, five differently sized specimens, included group I (dimension 5 × 1 cm), group II (5 × 2 cm), group III (5 × 3 cm), group IV (5 × 4 cm), and group V (5 × 5 cm) cut from commercial particleboard and medium-density fiberboard (MDF) (1.8 cm thick) were tested in compression shear. Only group V (5 × 5 cm) was prepared for the IB test. Results indicated that the compression shear strengths (CS) of particleboard and MDF, loaded in the horizontal or the diagonal direction, were greater than the IB, although a significant correlation existed between the two. This finding suggests that the IB of particleboard and MDF could be accurately estimated from the data collected by the CS test.