Recently multi-legged walking robots are widely developed. For these robots to walk safely, a sole sensor with high performance is desired. In the present paper, an arrayed type tactile sensor made of flexible silicone rubber, which is based on micro-electro-mechanical-systems (MEMS) technology, was developed. This sensor was applied as a sole sensor of a legged mobile robot. By processing the force data from many sensing elements using neural networks, information of contact force, i.e., three dimensional x, y, and z components of force vector, was able to be detected, which was confirmed by both simulation and experiment.