This paper reports an airflow shear stress sensor whose sensitivity is enhanced by modifying the surface roughness. The sensor consists of a cantilever-typed shear stress sensor and a micro pillar array on the surface of the cantilever. Piezoresistors are formed on the side walls of the cantilever's hinges to detect the shear force acting on the cantilever. When a shear airflow is applied to the proposed sensor, the shear force is generated on the surface of not only the cantilever but also the micro pillar array. Therefore, for the same airflow velocity, the total shear force acting on the surface of the proposed sensor is larger than that acting on the surface of a sensor with a flat surface. The experimental results show that the micro pillar structure improves the sensor sensitivity in response to airflow by 5 times compared with the flat surface structure.