We propose a highly sensitive three-dimensional tactile sensor using the structure of elastic micro pyramids pressing on piezoresistive cantilevers. In the structure of the sensor we proposed, the forces acting on the surface of the elastomer were transmitted to the cantilevers through the pyramids. The key point of our sensor was that the cantilevers were not completely embedded inside the elastomer: a cavity under each cantilever enabled the larger deformation and thus the larger resistance change of the cantilever. Therefore the high sensitivity of the sensor could be obtained. Moreover, by using four cantilevers aligned with four pyramids, the three-dimensional force sensor was realized. The sensitivities of our sensor to forces in normal and lateral directions were about 50 times and 2.4 times higher, respectively, compared to those of a tactile sensor with the ultrathin cantilevers embedded inside an elastomer .