We propose a muscle based bioactuator that can be driven in air. As the driving force of this actuator, we mounted aligned muscle fiber sheets between poles, with gold electrodes located at the edges of the muscle fibers to stimulate them. The muscle fibers are in a hollow space covered by a collagen structure to preserve the actuating properties in a wet condition. In the experiments, we prove that the muscle fiber sheets with striped patterns increase the forces by improving the alignment of muscle fibers, and the hollow space facilitates the contraction of muscle fibers smoothly. Owing to the collagen encapsulation, the muscle fibers were able to contract in wet condition even if the whole structure is in air; thus this bioactuator can bend in air. We believe that the bioactuator can be a useful module to construct soft robots as well as engineered tissue models for muscular cell biology and drug development.